Method for transceiving control signals, and apparatus therefor

ABSTRACT

A method is presented for transmitting an acknowledgement/negative acknowledgement (ACK/NACK) signal by a user equipment (UE) in a wireless communication system. The UE is configured with a primary cell (PCell) and a secondary cell (SCell). The UE receives downlink control information (DCI) via a physical downlink control channel (PDCCH). The DCI including a first field for transmit power control information and a second field for ACK/NACK resource offset information. The UE receives downlink data via a physical downlink shared channel (PDSCH) based on the DCI. The UE transmits an ACK/NACK signal for the downlink data using an ACK/NACK resource. When the downlink data is received on the PCell, the ACK/NACK resource is determined by adding a lowest resource index of the PDCCH and a value of the ACK/NACK resource offset information. When the downlink data is received on the SCell, the first field includes ACK/NACK resource indication information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of U.S. application Ser. No.14/404,375 filed on Nov. 26, 2014 (now U.S. Pat. No. 9,516,637 issued onDec. 6, 2016), which is the National Phase of PCT/KR2013/004827 filed onMay. 31, 2013, which claims priority under 35 U.S.C. 119(e) to U.S.Provisional Application Nos. 61/654,068 filed on May. 31, 2012;61/655,473 filed on Jun. 4, 2012; 61/657,006 filed on Jun. 7, 2012;61/695,288 filed on Aug. 30, 2012; 61/727,062 filed on Nov. 15, 2012;61/727,118 filed on Nov. 16, 2012, and 61/727,123 filed on Nov. 16,2012, all of which are hereby expressly incorporated by reference intothe present application.

BACKGROUND OF THE INVENTION

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for effectivelytransmitting and receiving an ACK/NACK resource information in awireless communication system.

Wireless communication systems are widely developed to provide a variouskinds of communication services such as audio or data service. Ingeneral, a wireless communication system is a multiple access systemcapable of supporting communications with multiple users by sharingavailable system resources (bandwidths, transmission power, etc.).Examples of the multiple access system include code division multipleaccess (CDMA) system, frequency division multiple access (FDMA) system,time division multiple access (TDMA) system, orthogonal frequencydivision multiple access (OFDMA) system, single carrier frequencydivision multiple access (SC-FDMA) system, multi-carrier frequencydivision multiple access (MC-FDMA) system, etc. In a wirelesscommunication system, a user equipment (UE) can receive information froma base station (BS) in downlink (DL) and transmit information to the BSin uplink (UL). The information transmitted or received by the UEincludes data and various control information and various physicalchannels are present according to the type and usage of the informationtransmitted or received by the UE.

SUMMARY OF THE INVENTION

An object of the present invention devised to solve the problem lies ina method and apparatus for effectively transmitting and receiving acontrol signal in a wireless communication system.

Another object of the present invention devised to solve the problemlies in a method and apparatus for effectively determining a resourcefor ACK/NACK signal transmission in a wireless communication system.

Another object of the present invention devised to solve the problemlies in a method and apparatus for preventing blocking of a resource fordownlink (DL) grant in a wireless communication system.

Another object of the present invention devised to solve the problemlies in a method and apparatus for reducing ACK/NACK resource signalingoverhead in a wireless communication system.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

In an aspect of the present invention, provided herein is a method fortransmitting an acknowledgement/negative acknowledgement (ACK/NACK)signal by a user equipment (UE) when a first carrier and a secondcarrier are aggregated in a wireless communication system, the methodcomprising receiving downlink control information including a firstfield for transmit power control information and a second field forresource allocation information via a physical downlink control channel;receiving downlink data using the resource allocation information; andtransmitting an ACK/NACK signal for the downlink data through anACK/NACK resource on the first carrier, wherein, when the downlink datais received on the first carrier, the downlink control informationfurther includes a third field and ACK/NACK resource offset informationis received through the third field, wherein, when the downlink data isreceived on the second carrier, ACK/NACK resource offset information isreceived through the first field, and wherein the ACK/NACK resource isdetermined using a lowest resource index of the physical downlinkcontrol channel and the ACK/NACK resource offset information.

Preferably, when the downlink data is received on the second carrier anda transmission mode of the ACK/NACK signal is configured as a physicaluplink control channel (PUCCH) format 3, the first field may includeACK/NACK resource indication information and the ACK/NACK resource maybe determined to be an ACK/NACK resource indicated by the ACK/NACKresource indication information from among a plurality of ACK/NACKresources configured through a higher layer.

Preferably, when the downlink control information and the downlink dataare received on the second carrier and a transmission mode of theACK/NACK signal is configured as channel selection, the first field mayinclude ACK/NACK resource indication information and the ACK/NACKresource may be determined to be an ACK/NACK resource indicated by theACK/NACK resource indication information from among a plurality ofACK/NACK resources configured through a higher layer.

Preferably, when the downlink control information is received on thefirst carrier, the downlink data is received on the second carrier and atransmission mode of the ACK/NACK signal is configured as channelselection, the ACK/NACK resource offset information may be receivedthrough the first field.

Preferably, when the downlink control information is received on thesecond carrier, the downlink control information may further include athird field for ACK/NACK resource information and the third field may beset to a predefined value.

In another aspect of the present invention, provided herein is a userequipment (UE) configured to transmit an acknowledgement/negativeacknowledgement (ACK/NACK) signal when a first carrier and a secondcarrier are aggregated in a wireless communication system, the UEcomprising: a radio frequency (RF) unit; and a processor, wherein theprocessor is configured to receive downlink control informationincluding a first field for transmit power control information and asecond field for resource allocation information via a physical downlinkcontrol channel, receive downlink data using the resource allocationinformation, and transmit an ACK/NACK signal for the downlink datathrough an ACK/NACK resource on the first carrier, wherein, when thedownlink data is received on the first carrier, the downlink controlinformation further includes a third field for ACK/NACK resourceinformation and ACK/NACK resource offset information is received throughthe third field, wherein, when the downlink data is received on thesecond carrier, ACK/NACK resource offset information is received throughthe first field, and wherein the ACK/NACK resource is determined using alowest resource index of the physical downlink control channel and theACK/NACK resource offset information.

Preferably, when the downlink data is received on the second carrier anda transmission mode of the ACK/NACK signal is configured as a physicaluplink control channel (PUCCH) format 3, the first field may includeACK/NACK resource indication information and the ACK/NACK resource maybe determined to be an ACK/NACK resource indicated by the ACK/NACKresource indication information from among a plurality of ACK/NACKresources configured through a higher layer.

Preferably, when the downlink control information and the downlink dataare received on the second carrier and a transmission mode of theACK/NACK signal is configured as channel selection, the first field mayinclude ACK/NACK resource indication information and the ACK/NACKresource may be determined to be an ACK/NACK resource indicated by theACK/NACK resource indication information from among a plurality ofACK/NACK resources configured through a higher layer.

Preferably, when the downlink control information is received on thefirst carrier, the downlink data is received on the second carrier and atransmission mode of the ACK/NACK signal is configured as channelselection, the ACK/NACK resource offset information may be receivedthrough the first field.

Preferably, when the downlink control information is received on thesecond carrier, the downlink control information may further include athird field for ACK/NACK resource information and the third field may beset to a predefined value.

According to the present invention, a control signal can be effectivelytransmitted and received in a wireless communication system.

According to the present invention, a resource for ACK/NACK signaltransmission can be effectively determined in a wireless communicationsystem.

According to the present invention, blocking of a resource for downlink(DL) grant can be prevented in a wireless communication system.

According to the present invention, ACK/NACK resource signaling overheadcan be reduced in a wireless communication system.

It will be appreciated by persons skilled in the art that that theeffects that could be achieved with the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

FIG. 1 illustrates physical channels and a general method fortransmitting signals on the physical channels in the LTE(-A) system,

FIG. 2, including views (a) and (b), illustrates a structure of a radioframe used in an LTE(-A) system,

FIG. 3 illustrates a resource grid of one DL slot used in an LTE(-A)system,

FIG. 4 illustrates a downlink subframe structure used in the LTE(-A)system,

FIG. 5 illustrates a control channel allocated to a downlink subframe,

FIG. 6 illustrates a structure of a UL subframe in the LTE(-A) system,

FIGS. 7 and 8 show a slot level structure of PUCCH format 1a/1b,

FIG. 9 shows an example of determining PUCCH resources for ACK/NACK,

FIG. 10 is a diagram illustrating a transmitting procedure of TDD ULACK/NACK in a single cell situation,

FIG. 11 illustrates an example of ACK/NACK transmission using DL DAI,

FIG. 12 illustrates a carrier aggregation (CA) communication system,

FIG. 13 illustrates an exemplary scheduling, when a plurality ofcarriers are aggregated,

FIG. 14 illustrates exemplary PUCCH format 3 at a slot level,

FIG. 15 illustrates exemplary PUCCH format 3 at a subframe level,

FIG. 16 is a diagram illustrating an example in which a DL physicalchannel is allocated to a subframe,

FIG. 17 illustrates resource allocation for an E-PDCCH and an E-PDCCHreceiving procedure,

FIG. 18 illustrates an example for determining a PUCCH resource in thecase of the SORTD method or the channel selection method,

FIG. 19 illustrates resource blocking,

FIG. 20 illustrates a method for determining two PUCCH resourcesaccording to the present invention,

FIG. 21 illustrates a method for determining two PUCCH resourcesaccording to the present invention,

FIG. 22 illustrates an example for determining two PUCCH resourcesaccording to the present invention,

FIG. 23 is a flowchart of a method for signaling ACK/NACK resourceinformation according to the present invention, and

FIG. 24 is a diagram illustrating a BS and a UE to which the presentinvention is applicable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following embodiments of the present invention can be applied to avariety of wireless access technologies, for example, code divisionmultiple access (CDMA), frequency division multiple access (FDMA), timedivision multiple access (TDMA), orthogonal frequency division multipleaccess (OFDMA), single carrier frequency division multiple access(SC-FDMA), and the like. CDMA may be embodied through wireless (orradio) technology such as universal terrestrial radio access (UTRA) orCDMA2000. TDMA may be embodied through wireless (or radio) technologysuch as global system for mobile communication (GSM)/general packetradio service (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMAmay be embodied through wireless (or radio) technology such as instituteof electrical and electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE 802-20, and evolved UTRA (E-UTRA). UTRA is a partof universal mobile telecommunications system (UMTS). 3^(rd) generationpartnership project (3GPP) long term evolution (LTE) is a part of E-UMTS(Evolved UMTS), which uses E-UTRA. LTE-Advanced (LTE-A) is an evolvedversion of 3GPP LTE. Throughout this specification, the LTE system maybe referred to as a system according to 3^(rd) generation partnershipproject (3GPP) technical specification (TS) 36 8 (Release 8). Inaddition, in this specification, the LTE-A system may be referred to asa system according to 3GPP TS 36 series Release 9 and 10. The LTE(-A)system may be called to include the LTE system and the LTE-A system. Forclarity, the following description focuses on 3GPP LTE(-A) system.However, technical features of the present invention are not limitedthereto.

In a mobile communication system, a UE may receive information from a BSin downlink and transmit information in uplink. The informationtransmitted or received by the UE may be data and various controlinformation. In addition, there are various physical channels accordingto the type or use of the information transmitted or received by the UE.

FIG. 1 illustrates physical channels and a general method fortransmitting signals on the physical channels in the LTE(-A) system.

When a UE is powered on or enters a new cell, the UE performs initialcell search in step S101. The initial cell search involves acquisitionof synchronization to an eNB. To this end, the UE synchronizes itstiming to the eNB and acquires information such as a cell identifier(ID) by receiving a primary synchronization channel (P-SCH) and asecondary synchronization channel (S-SCH) from the eNB. Then the UE mayacquire broadcast information in the cell by receiving a physicalbroadcast channel (PBCH) from the eNB. During the initial cell search,the UE may monitor a DL channel state by receiving a downlink referencesignal (DL RS).

After the initial cell search, the UE may acquire more detailed systeminformation by receiving a physical downlink control channel (PDCCH) andreceiving a physical downlink shared channel (PDSCH) based oninformation of the PDCCH in step S102.

To complete access to the eNB, the UE may perform a random accessprocedure such as steps S103 to S106 with the eNB. To this end, the UEmay transmit a preamble on a physical random access channel (PRACH)(S103) and may receive a response message to the preamble on a PDCCH anda PDSCH associated with the PDCCH (S104). In the case of acontention-based random access, the UE may additionally perform acontention resolution procedure including transmission of an additionalPRACH (S105) and reception of a PDCCH signal and a PDSCH signalcorresponding to the PDCCH signal (S106).

After the above procedure, the UE may receive a PDCCH and/or a PDSCHfrom the eNB (S107) and transmit a physical uplink shared channel(PUSCH) and/or a physical uplink control channel (PUCCH) to the eNB(S108), in a general UL/DL signal transmission procedure. Informationthat the UE transmits to the eNB is called Uplink Control Information(UCI). The UCI includes hybrid automatic repeat and requestacknowledgement/negative acknowledgement (HARQ-ACK/NACK), schedulingrequest (SR), channel state information (CSI), etc. The CSI includeschannel quality indicator (CQI), precoding matrix indicator (PMI), rankindication (RI), etc. UCI is generally transmitted on a PUCCHperiodically. However, if control information and traffic data should betransmitted simultaneously, they may be transmitted on a PUSCH. Inaddition, the UCI may be transmitted aperiodically on the PUSCH, uponreceipt of a request/command from a network.

FIG. 2, including views (a) and (b), illustrates a structure of a radioframe used in an LTE(-A) system. In a cellular OFDM radio packetcommunication system, uplink/downlink data packet transmission isperformed in subframe units and one subframe is defined as apredetermined duration including a plurality of OFDM symbols. TheLTE(-A) standard supports a type-1 radio frame structure applicable tofrequency division duplex (FDD) and a type-2 radio frame structureapplicable to time division duplex (TDD).

FIG. 2(a) shows the structure of the type-1 radio frame. A downlinkradio frame includes 10 subframes and one subframe includes two slots ina time domain. A time required to transmit one subframe is referred toas a transmission time interval (TTI). For example, one subframe has alength of 1 ms and one slot has a length of 0.5 ms. One slot includes aplurality of OFDM symbols in a time domain and includes a plurality ofresource blocks (RBs) in a frequency domain. In the LTE(-A) system,since OFDMA is used in downlink, an OFDM symbol indicates one symbolperiod. The OFDM symbol may be referred to as an SC-FDMA symbol orsymbol period. A RB as a resource assignment unit may include aplurality of consecutive subcarriers in one slot.

The number of OFDM symbols included in one slot may be changed accordingto the configuration of a cyclic prefix (CP). The CP includes anextended CP and a normal CP. For example, if OFDM symbols are configuredby the normal CP, the number of OFDM symbols included in one slot may be7. If OFDM symbols are configured by the extended CP, since the lengthof one OFDM symbol is increased, the number of OFDM symbols included inone slot is less than the number of OFDM symbols in case of the normalCP. In case of the extended CP, for example, the number of OFDM symbolsincluded in one slot may be 6. In the case where a channel state isunstable, such as the case where a UE moves at a high speed, theextended CP may be used in order to further reduce inter-symbolinterference.

In case of using the normal CP, since one slot includes seven OFDMsymbols, one subframe includes 14 OFDM symbols. At this time, a maximumof first two or three OFDM symbols of each subframe may be assigned to aphysical downlink control channel (PDCCH) and the remaining OFDM symbolsmay be assigned to a physical downlink shared channel (PDSCH).

FIG. 2(b) shows the structure of the type-2 radio frame. The type-2radio frame includes two half frames and each half frame includes fivesubframes, a downlink pilot time slot (DwPTS), a guard period (GP) andan uplink pilot time slot (UpPTS). One subframe includes two slots. Forexample, a downlink slot (e.g., DwPTS) is used for initial cell search,synchronization or channel estimation of a UE. For example, an uplinkslot (e.g., UpPTS) is used for channel estimation of a BS and uplinktransmission synchronization of a UE. For example, the uplink slot(e.g., UpPTS) may be used to transmit a sounding reference signal (SRS)for channel estimation in an eNB and to transmit a physical randomaccess channel (PRACH) that carriers a random access preamble for uplinktransmission synchronization. The GP is used to eliminate interferencegenerated in uplink due to multi-path delay of a downlink signal betweenuplink and downlink. Table 1 below shows an uplink (UL)-downlink (DL)configuration in subframes in a radio frame in a TDD mode.

Uplink- Downlink- downlink to-Uplink config- Switch-point Subframenumber uration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U D S U UU 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms  D S U UU D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D D D D D 65 ms D S U U U D S U U D.

In Table 1 above, D represents a DL subframe, U represents a ULsubframe, and S represents a special subframe. The special subframeincludes a downlink pilot timeslot (DwPTS), a guard period (GP), and anuplink pilot timeslot (UpPTS). Table 2 below shows a special subframeconfiguration.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Normal Extended Normal Extended Special subframecyclic prefix cyclic prefix cyclic prefix cyclic prefix configurationDwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192· T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —.

The above-described radio frame structure is purely exemplary and thusthe number of subframes in a radio frame, the number of slots in asubframe, or the number of symbols in a slot may vary in different ways.

FIG. 3 illustrates a resource grid of one DL slot used in an LTE(-A)system.

Referring to FIG. 3, a DL slot includes a plurality of OFDM symbols inthe time domain. One DL slot may include 7 OFDM symbols and a resourceblock (RB) may include 12 subcarriers in the frequency domain. However,the present invention is not limited thereto. Each element of theresource grid is referred to as a Resource Element (RE). An RB includes12×7 REs. The number of RBs in a DL slot, N^(DL) depends on a DLtransmission bandwidth. A UL slot may have the same structure as a DLslot.

FIG. 4 illustrates a downlink subframe structure used in the LTE(-A)system.

Referring to FIG. 4, a maximum of three (four) OFDM symbols located in afront portion of a first slot within a subframe correspond to a controlregion to which a control channel is allocated. The remaining OFDMsymbols correspond to a data region to which a physical downlink sharedchancel (PDSCH) is allocated. A basic resource unit of the data regionis RB. Examples of downlink control channels used in the LTE(-A) systeminclude a physical control format indicator channel (PCFICH), a physicaldownlink control channel (PDCCH), a physical hybrid ARQ indicatorchannel (PHICH), etc.

FIG. 5 illustrates a control channel allocated to a downlink subframe.In FIGS. 5, R1 to R4 denote a cell-specific reference signal (CRS) or acell-common reference signal for antenna ports 0 to 3. The CRS istransmitted in all bands every subframe and fixed in a predeterminedpattern in a subframe. The CRS is used to channel measurement anddownlink signal demodulation.

Referring to FIG. 5, the PCFICH is transmitted at a first OFDM symbol ofa subframe and carries information regarding the number of OFDM symbolsused for transmission of control channels within the subframe. ThePCFICH is composed of four REGs that are uniformly distributed in acontrol region based on a cell ID. The PCFICH indicates a value of 1 to3 (or 2 to 4) and is modulated via quadrature phase shift keying (QPSK).The PHICH is a response of uplink transmission and carries an HARQacknowledgment (ACK)/not-acknowledgment (NACK) signal. The PHICH exceptfor CRS and PCFICH (a first OFDM symbol) is allocated on the remainingREGs in one or more OFDM symbols configured by PHICH duration. The PHICHis allocated to three REGs that are distributed if possible on thefrequency domain.

The PDCCH is allocated in first n OFDM symbols (hereinafter, a controlregion) of a subframe. Here, n is an integer equal to or greater than 1and is indicated by the PCFICH. Control information transmitted throughthe PDCCH is referred to as downlink control information (DCI). DCIformat is defined as formats 0, 3, 3A, and 4 for uplink and defined asformats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, and 2D for downlink. DCIformat optionally includes information about hopping flag, RBallocation, modulation coding scheme (MCS), redundancy version (RV), newdata indicator (NDI), transmit power control (TPC), cyclic shiftdemodulation reference signal (DM-RS), channel quality information (CQI)request, HARQ process number, transmitted precoding matrix indicator(TPMI), precoding matrix indicator (PMI) confirmation, etc. according toits usage.

A PDCCH may carry a transport format and a resource allocation of adownlink shared channel (DL-SCH), resource allocation information of anuplink shared channel (UL-SCH), paging information on a paging channel(PCH), system information on the DL-SCH, information on resourceallocation of an upper-layer control message such as a random accessresponse transmitted on the PDSCH, a set of Tx power control commands onindividual UEs within an arbitrary UE group, a Tx power control command,information on activation of a voice over IP (VoIP), etc. A plurality ofPDCCHs can be transmitted within a control region. The UE can monitorthe plurality of PDCCHs. The PDCCH is transmitted on an aggregation ofone or several consecutive control channel elements (CCEs). The CCE is alogical allocation unit used to provide the PDCCH with a coding ratebased on a state of a radio channel. The CCE corresponds to a pluralityof resource element groups (REGs). A format of the PDCCH and the numberof bits of the available PDCCH are determined by the number of CCEs. TheBS determines a PDCCH format according to DCI to be transmitted to theUE, and attaches a cyclic redundancy check (CRC) to control information.The CRC is masked with a unique identifier (referred to as a radionetwork temporary identifier (RNTI)) according to an owner or usage ofthe PDCCH. If the PDCCH is for a specific UE, a unique identifier (e.g.,cell-RNTI (C-RNTI)) of the UE may be masked to the CRC. Alternatively,if the PDCCH is for a paging message, a paging identifier (e.g.,paging-RNTI (P-RNTI)) may be masked to the CRC. If the PDCCH is forsystem information (more specifically, a system information block(SIB)), a system information RNTI (SI-RNTI) may be masked to the CRC.When the PDCCH is for a random access response, a random access-RNTI(RA-RNTI) may be masked to the CRC.

A plurality of PDCCHs may be transmitted in one subframe. Each PDCCH istransmitted using one or more control channel elements (CCEs) and eachCCE corresponds to nine sets of four resource elements. The fourresource elements are referred to as a resource element group (REG).Four QPSK symbols are mapped to one REG. A resource element allocated toa reference signal is not included in an REG and thus a total number ofREGs in a given OFDM symbol varies according to whether a cell-specificreference signal is present.

Table 3 shows the number of CCEs, the number of REGs, and the number ofPDCCH bits according to PDCCH format.

TABLE 3 PDCCH Number of Number of Number of PDCCH format CCE (n) REGbits 0 1 9 72 1 2 18 144 2 4 36 288 3 8 72 576.

CCEs are sequentially numbered. To simplify a decoding process,transmission of a PDCCH having a format including n CCEs can be startedusing as many CCEs as a multiple of n. The number of CCEs used totransmit a specific PDCCH is determined by a BS according to channelcondition. For example, if a PDCCH is for a UE having a high-qualitydownlink channel (e.g. a channel close to the BS), only one CCE can beused for PDCCH transmission. However, for a UE having a poor channel(e.g. a channel close to a cell edge), 8 CCEs can be used for PDCCHtransmission in order to obtain sufficient robustness. In addition, apower level of the PDCCH can be controlled according to channelcondition.

The LTE(-A) system defines a limited set of CCE positions in which aPDCCH is to be positioned for each UE. A limited set of CCE positionsthat a UE can find a PDCCH of the UE may be referred to as a searchspace (SS). In the LTE(-A) system, the SS has different sizes accordingto each PDCCH format. In addition, a UE-specific SS and a common SS areseparately defined. The BS does not provide the UE with informationindicating where the PDCCH is located in the control region.Accordingly, the UE monitors a set of PDCCH candidates within thesubframe and finds its own PDCCH. The term “monitoring” means that theUE attempts to decode the received PDCCHs according to respective DCIformats. The monitoring for a PDCCH in an SS is referred to as blinddecoding (blind detection). Through blind decoding, the UEsimultaneously performs identification of the PDCCH transmitted to theUE and decoding of the control information transmitted through thecorresponding PDCCH. For example, in the case where the PDCCH isdemasked using the C-RNTI, the UE detects its own PDCCH if a CRC erroris not detected. The USS is separately configured for each UE and ascope of CSSs is known to all UEs. The USS and the CSS may be overlappedwith each other. When a significantly small SS is present, if some CCEpositions are allocated in an SS for a specific UE, the remaining CCEsare not present. Thus a BS may not find CCE resources in which the PDCCHis to be transmitted to all available UEs in a given subframe. In orderto minimize the possibility that such blocking is subsequent to a nextsubframe, a start position of the USS is UE-specifically hopped.

Table 4 shows sizes of CSS and USS.

TABLE 4 PDCCH Number of Number of Number of format CCE (n) candidates inCSS candidates in USS 0 1 — 6 1 2 — 6 2 4 4 2 3 8 2  2.

To control computational load of blind decoding based on the number ofblind decoding processes to an appropriate level, the UE is not requiredto simultaneously search for all defined DCI formats. In general, the UEsearches for formats 0 and 1A at all times in the UE-specific searchspace. Formats 0 and 1A have the same size and are discriminated fromeach other by a flag in a message. The UE may need to receive anadditional format (e.g. format 1, 1B or 2 according to PDSCHtransmission mode set by a BS). The UE searches for formats 1A and 1C inthe UE-common search space. Furthermore, the UE may be set to search forformat 3 or 3A. Formats 3 and 3A have the same size as that of formats 0and 1A and may be discriminated from each other by scrambling CRC withdifferent (common) identifiers rather than a UE-specific identifier. APDSCH transmission scheme and information contents of DCI formatsaccording to a transmission mode will be listed below.

Transmission Mode (TM)

-   -   Transmission Mode 1: Transmission from a single eNB antenna port    -   Transmission Mode 2: Transmit diversity    -   Transmission Mode 3: Open-loop spatial multiplexing    -   Transmission Mode 4: Closed-loop spatial multiplexing    -   Transmission Mode 5: Multi-user MIMO    -   Transmission Mode 6: Closed-loop rank-1 precoding    -   Transmission Mode 7: Single-antenna port (port 5) transmission    -   Transmission Mode 8: Dual layer transmission (ports 7 and 8) or        single-antenna port (port 7 or 8) transmission    -   Transmission Modes 9 and 10: Layer transmission up to rank 8        (ports 7 to 14) or single-antenna port (port 7 or 8)        transmission

DCI Format

-   -   Format 0: Resource grant for PUSCH transmission (uplink)    -   Format 1: Resource allocation for single codeword PUSCH        transmission (transmission modes 1, 2, and 7)    -   Format 1A: Compact signaling of resource allocation for single        codeword PDSCH transmission (all modes)    -   Format 1B: Compact resource allocation for PDSCH (mode 6) using        rank-1 closed-loop precoding    -   Format 1C: Very compact resource allocation for PDSCH (e.g.,        paging/broadcast system information)    -   Format 1D: Compact resource allocation for PDSCH (mode 5) using        multi-user MIMO    -   Format 2: Resource allocation for PDSCH (mode 4) of closed-loop        MIMO operation    -   Format 2A: Resource allocation for PDSCH (mode 3) of open-loop        MIMO operation    -   Format 3/3A: Power control command with 2-bit/1-bit power        adjustments for PUCCH and PUSCH    -   Format 4: Resource grant for PUSCH transmission (uplink) in a        cell configured in a multi-antenna port transmission mode

A UE may be semi-statically configured via higher layer signaling forreception of PDSCH data transmission that is scheduled through the PDCCHaccording to ten transmission modes. Table 5 below shows a transmissionmode signaled via a higher layer and configurable DCI format when a UEdetects a scrambled PDCCH as a C-RNTI identifier.

FIG. 6 illustrates a structure of a UL subframe in the LTE(-A) system.

Referring to FIG. 6, a UL subframe includes a plurality of (e.g. 2)slots. A slot may include a different number of SC-FDMA symbolsaccording to a CP length. The UL subframe is divided into a controlregion and a data region in the frequency domain. The data regionincludes a PUSCH to transmit a data signal such as voice and the controlregion includes a PUCCH to transmit UCI. The PUCCH occupies a pair ofRBs at both ends of the data region on a frequency axis and the RB pairfrequency-hops over a slot boundary.

The PUCCH may deliver the following control information.

-   -   Scheduling request (SR): information requesting UL-SCH        resources. An SR is transmitted in On-Off Keying (OOK).    -   HARQ ACK/NACK: a response signal to a DL data packet received on        a PDSCH, indicating whether the DL data packet has been received        successfully. A 1-bit ACK/NACK is transmitted as a response to a        single DL codeword and a 2-bit ACK/NACK is transmitted as a        response to two DL codewords.    -   CSI: feedback information regarding a DL channel. CSI includes a        CQI and Multiple Input Multiple Output (MIMO)-related feedback        information includes an RI, a PMI, a Precoding Type Indicator        (PTI), etc. The CSI occupies 20 bits per subframe.

Table 5 below illustrates a mapping relationship between PUCCH formatsand UCI in the LTE system.

TABLE 5 PUCCH format Uplink Control Information, UCI Format 1SR(Scheduling Request) (un-modulated waveform) Format 1a 1-bit HARQACK/NACK (with/without SR) Format 1b 2-bit HARQ ACK/NACK (with/withoutSR) Format 2 CSI (20 coded bits) Format 2 CSI and ½-bit HARQ ACK/NACK(20 bits) (Extended CP only) Format 2a CSI and 1-bit HARQ ACK/NACK (20 +1 coded bits) Format 2b CSI and 2-bit HARQ ACK/NACK (20 + 2 coded bits)Format 3 HARQ ACK/NACK + SR (48 bits). (LTE-A)

Meanwhile, in the LTE system, since the UE cannot simultaneouslytransmit a PUCCH and a PUSCH, when UCI (e.g., CQI/PMI, HARQ-ACK, RI,etc.) needs to be transmitted in a subframe in which a PUSCH istransmitted, UCI is multiplexed in a PUSCH region. Multiplexing of UCIin a PUSCH region may be referred to as PUSCH piggyback. In the LTE-Asystem, the UE may also be configured not to simultaneously transmit aPUCCH and a PUSCH. In this case, when UCI (e.g., CQI/PMI, HARQ-ACK, RI,etc.) needs to be transmitted in a subframe in which a PUSCH istransmitted, the UE may multiplex UCI in a PUSCH region (PUSCHpiggyback).

FIGS. 7 and 8 show a slot level structure of PUCCH format 1a/1b. FIG. 7shows the case of normal CP and FIG. 8 shows the case of extended CP.The PUCCH format 1a/1b is used for ACK/NACK transmission. In the case ofnormal CP, SC-FDMA symbols #2, #3, and #4 are used for DM RStransmissions. In the case of extended CP, SC-FDMA symbols #2 and #3 areused for DM RS transmission. Accordingly, four SC-FDMA symbols are usedfor ACK/NACK transmission in one slot. Throughout this specification,the PUCCH format 1a/1b is referred to as PUCCH format 1 unless clearlyspecified otherwise in context.

Referring to FIGS. 7 and 8, one ACK/NACK information bit [b(o)] and twoACK/NACK information bits [(b0)b(1)] are modulated using binary phaseshift keying (BPSK) and quadrature phase shift keying (QPSK) modulationrespectively, resulting in a single ACK/NACK modulation symbol (d0).Each bit [b(i), i=0, 1] in the ACK/NACK information represents aHARQ-ACK response to a corresponding DL transmission block (orcodeword). A positive ACK (ACK) is encoded as a binary ‘1’ and anegative ACK (NAKC) as a binary ‘0’. Table 6 shows a modulation tabledefined for the PUCCH formats 1a and 1b in legacy LTE/LTE-A.

In PUCCH format 1, control information having the same content isrepeated in slot units in a subframe. In each UE, an ACK/NACK signal istransmitted through different resources configured with different cyclicshift (CS) (frequency domain code) of a computer-generated constantamplitude zero auto correlation (CG-CAZAC) sequence and an orthogonalcover or orthogonal cover code (OC or OCC) (time domain spreading code).The OC includes, for example, Walsh)/DFT orthogonal code. When thenumber of CSs is 6 and the number of OCs is 3, a total of 18 UEs may bemultiplexed on the same PRB based on a single antenna. Orthogonalsequences w0, w1, w2, and w3 (after FFT modulation) may be applied in arandom time domain or a random frequency domain (before FFT modulation).

RSs transmitted from different UEs are multiplexed in the same way asUCI. The number of cyclic shifts supported in an SC-FDMA symbol forPUCCH ACK/NACK RBs is configurable by a cell-specific higher-layersignaling parameter. ε{1, 2, 3} indicates 12, 6, or 4 shiftsrespectively. For the time-domain CDM, the number of spreading codes forACK/NACK data is limited by the number of RS symbols, as themultiplexing capacity of RS symbols is smaller than that of USI symbolsdue to smaller number of RS symbols.

FIG. 9 shows an example of determining PUCCH resources for ACK/NACK. APUCCH resource for ACK/NACK information is not allocated to each UE inthe cell in advance in the LTE system, and a plurality of UEs in thecell share a plurality of PUCCH resources at each point of time.Specifically, a PUCCH resource that a UE uses to transmit the ACK/NACKcorresponds to a PDCCH that carries scheduling information regardingcorresponding downlink data. In detail, a PDCCH transmitted o the UE ina downlink subframe is configured with one or more control channelelements (CCEs) and ACK/NACK may be transmitted through a PUCCH resourcecorresponding to a specific CCE (e.g., first CCE) among the CCEsconstructing the corresponding PDCCH.

Referring to FIG. 9, each square of a DL Component Carrier (CC)represents a CCE and each square of a UL CC represents a PUCCH resource.Each PUCCH index indicates a PUCCH resource for an ACK/NACK. Ifinformation about a PDSCH is delivered on a PDCCH including CCEs 4, 5,and 6 as illustrated in FIG. 8, the UE transmits an ACK/NACK in PUCCH 4mapped to CCE 4 which is the first of the CCEs of the PDCCH. FIG. 9illustrates an exemplary case in which there are up to M PUCCHs in a ULCC, for a DL CC having up to N CCEs. While N may be equal to M, N and Mmay be different and thus the CCEs may be mapped to the PUCCHs in anoverlapped manner.

Specifically, PUCCH resource indexes are determined by the followingequation in the LTE system.n _(PUCCH) ⁽¹⁾ =n _(CCE) +N _(PUCCH) ⁽¹⁾  [Equation 1]

Here, n⁽¹⁾ _(PUCCH) is a resource index in PUCCH format 1, fortransmission of ACK/NACK/DTX, N⁽¹⁾ _(PUCCH) is a value signaled viahigher-layer signaling, and n_(CCE) is the lowest index of CCE indexesused for PDCCH transmission. A cyclic shift, an orthogonal cover code(or a orthogonal spreading code), and a physical resource block (PRB)for PUCCH format 1 are acquired from n⁽¹⁾ _(PUCCH).

FIG. 10 is a diagram illustrating a transmitting procedure of TDD ULACK/NACK in a single cell situation.

Referring to FIG. 10, a UE may receive one or more DL transmissions(e.g., PDSCH signal) on M DL subframes (SFs) (S1002_0 to S1002_M−1).Each PDSCH signal I used to transmit one or more (e.g., 2) transportblocks (TBs) (or a codeword (CW)) according to a transmission mode.Although not illustrated in FIG. 10, in steps S1002_0 to S1002_M−1, aPDCCH signal that requires an ACK/NACK response, for example, a PDCCHsignal (simply, SPS release PDCCH signal) indicating SPS release mayalso be received. When a PDSCH signal and/or an SPS release PDCCH signalare present in M DL subframes, the UE transmits ACK/NACK through one ULsubframe corresponding M DL subframes via a procedure (e.g., ACK/NACK(payload) generation, ACK/NACK resource allocation, etc.) fortransmitting ACK/NACK (S1004). ACK/NACK includes reception responseinformation for a PDSCH signal and/or an SPS release PDCCH signal ofsteps S1002_0 to S1002_M−1. Although ACK/NACK can be basicallytransmitted through a PUCCH (e.g., refer to FIGS. 7 and 8), when PUSCHis transmitted at a point of time of ACK/NACK transmission, the ACK/NACKmay be transmitted through a PUSCH. Various PUCCH formats of Table 3 maybe used for ACK/NACK transmission. In addition, in order to reduce thenumber of transmitted ACK/NACK bits, various methods such as ACK/NACKbundling, ACK/NACK channel selection, etc. may be used.

As described above, in TDD, ACK/NACK for data received in M DL subframesis transmitted through one UL subframe (i.e., M DL SF(s):1 UL SF), arelation thereof is given by a downlink association set index (DASI).

Table 6 below shows DASI (K:{k0,k1, . . . kM−1}) defined in LTE(-A).Table 6 shows an interval with a DL subframe associated with a ULsubframe in which ACK/NACK is transmitted in terms of the UL subframe.In detail, when PDSCH transmission and/or SPS release PDCCH are presentin a subframe n−k (kεK), a UE transmits ACK/NACK corresponding to asubframe n.

TABLE 6 UL-DL Subframe n Configuration 0 1 2 3 4 5 6 7 8 9 0 — — 6 — 4 —— 6 — 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, 4, 6 — — — — 8, 7, 4, 6— — 3 — — 7, 6, 11 6, 5 5, 4 — — — — — 4 — — 12, 8, 7, 11 6, 5, 4, 7 — —— — — — 5 — — 13, 12, 9, 8, 7, 5, 4, 11, 6 — — — — — — — 6 — — 7 7 5 — —7 7 —.

During an operation using a TDD method, a UE needs to transmit anACK/NACK signal for one or more DL transmissions (e.g., PDSCH) receivedthrough M DL SFs through one UL SF. ACK/NACK for a plurality of DL SFsis transmitted through one UL SF using the following method.

1) ACK/NACK bundling: ACK/NACK bits for a plurality of data units (e.g.,PDSCH, SPS release PDCCH, etc.) are combined via logical operation(e.g., logical-AND operation). For example, when all data units aresuccessfully decoded, a receiver (e.g., UE) transmits an ACK signal. Onthe other hand, when decoding (or detecting) of even one data unitfails, the receiver may or may not transmit a NACK signal.

2) Channel selection: A UE that receives a plurality of data units(e.g., PDSCH, SPS release PDCCH, etc.) occupies a plurality of PUCCHresources for ACK/NACK transmission. An ACK/NACK response for aplurality of data units is identified by a combination of a PUCCHresource used for actual ACK/NACK transmission and transmitted ACK/NACKcontent (e.g., a bit value and a QPSK symbol value). The channelselection method may also be referred to as an ACK/NACK selection methodor a PUCCH selection method.

In TDD, upon transmitting an ACK/NACK signal to an eNB, a UE may misssome of PDCCH(s) transmitted by the eNB for a plurality of subframeperiods. In this case, the UE cannot know that a PDSCH corresponding tothe missed PDCCH is transmitted o the UE, and thus errors may occurduring ACK/NACK generation.

To overcome these errors, a TDD system adds a downlink assignment index(DAI) to a PDCCH. The DAI denotes accumulated values (i.e., a countingvalue) of PDCCH(s) corresponding to PDSCH(s) to a current subframe in DLsubframe(s) n−k (k⊂K) and PDCCH(s) indicating DL SPS release. Forexample, when three DL subframes correspond to one UL subframe, indexesare sequentially applied (i.e., sequentially counted) to a PDSCHtransmitted in three DL subframe periods to carry a PDCCH for schedulinga PDSCH. The UE may recognize whether a PDCCH has been appropriatelyreceived so far from the DAI information in the PDCCH. For convenience,DAI included in PDSCH-scheduling PDCCH and SPS release PDCCH is referredto as DL DAI or DAI-counter (DAI-c) or is simply referred to as DAI.

Table 7 below shows a value V^(DL) _(DAI) indicated by a DL DAI field.In this specification, DL DAI may be simply denoted by V. MSB indicatesa most significant bit and LSB indicates a least significant bit.

TABLE 7 Number of subframes with PDSCH DAI transmission and with PDCCHMSB, LSB V_(DAI) ^(DL) indicating DL SPS release 0, 0 1 1 or 5 or 9 0, 12 2 or 6 1, 0 3 3 or 7 1, 1 4 0 or 4 or 8.

FIG. 11 illustrates an example of ACK/NACK transmission using DL DAI.

This example assumes a TDD system configured with three DL subframes:one UL subframe. For convenience, it is assumed that a UE transmitsACK/NACK using a PUSCH resource. In the legacy LTE, when ACK/NACK istransmitted through a PUSCH, 1-bit or 2-bit bundled ACK/NACK istransmitted.

Referring to FIG. 11, like in the first example, when a second PDCCH ismissed, a value of DL DAI of a third PDCCH is different from the numberof PDCCHs that have been detected so far, and thus a UE may recognizethat a second PDCCH is missed. In this case, a UE may process anACK/NACK response for a second PDCCH as NACK (or NACK/DTX). On the otherhand, like in the second example, when a last PDCCH is missed, a valueof DL DAI of a lastly detected PDCCH is the same as the number of PDCCHsthat have been detected so far, and thus the UE may not recognize thatthe last PDCCH is missed (i.e., DTX). Accordingly, the UE recognizesthat only two PDCCHs are scheduled for a DL subframe period. In thiscase, the UE bundles only ACK/NACK corresponding to first two PDCCHs,and thus errors occur in an ACK/NACK feedback procedure. To overcomethis problem, PUSCH-scheduling PDCCH (i.e., UL grant PDCCH) includes aDAI field (for convenience, a UL DAI field). The UL DAI field is a 2-bitfield and the UL DAI field indicates information about the number ofscheduled PDCCHs.

In detail, when V^(UL) _(DAI)≠(U_(DAI)+N_(SPS)−1)mod 4+1, the UE assumesthat at least one DL allocation is lost (i.e., DTX generation) andgenerates NACK for all code words according to a bundling procedure.Here, U_(DAI) indicates a total number of SPS release PDCCH and DL grantPDCCHs detected in a subframe n−k (k⊂K) (refer to Table 6). N_(SPS)denotes the number of SPS PDSCHs and is 0 or 1.

Table 8 below shows a value V^(UL) _(DAI) indicated by a UL DAI field.In this specification, UL DAI may be simply denoted by W. MSB indicatesa most significant bit and LSB indicates a least significant bit.

TABLE 8 Number of subframes with PDSCH DAI transmission and with PDCCHMSB, LSB V_(DAI) ^(UL) indicating DL SPS release 0, 0 1 1 or 5 or 9 0, 12 2 or 6 1, 0 3 3 or 7 1, 1 4 0 or 4 or 8.

FIG. 12 illustrates a carrier aggregation (CA) communication system. AnLTE-A system uses carrier aggregation or bandwidth aggregationtechnologies using a greater UL/DL bandwidth by collecting a pluralityof UL/DL frequency blocks in order to use wider frequency band. Eachfrequency block is transmitted using a component carrier (CC). A CC maybe understood as a carrier frequency (a center carrier or a centerfrequency) for a corresponding frequency block.

Referring to FIG. 12, a plurality of UL/DL CCs may be collected tosupport a wider UL/DL bandwidth. The CCs may or may not be adjacent toeach other in the frequency domain. Bandwidths of CCs may beindependently determined. Asymmetric carrier aggregation in which thenumber of UL CCs and the number of DL CCs are different may be possible.For example, in the case of two DL CCs and one UL CC, asymmetric carrieraggregation may be configured with 2:1. A DL CC/UL CC link may be fixedto a system and may be semi-statically configured. In addition, even ifan entire band of a system is configured by N CCs, a frequency band formonitoring/receiving of a specific UE may be limited to M(<N) CCs.Various parameters for carrier aggregation may be configuredcell-specifically, UE group-specifically, or UE-specifically. Controlinformation may be configured to be transmitted and received throughonly a specific CC. The specific CC may be referred to as a primary CC(PCC) (or anchor CC) and the remaining CC may be referred to as asecondary CC (SCC).

The LTE(-A) system adopts the concept of cell to manage radio resources.A cell is defined as a combination of DL and UL resources, while the ULresources are optional. Accordingly, a cell may include DL resourcesonly or both DL and UL resources. If CA is supported, the linkagebetween the carrier frequencies (or DL CCs) of DL resources and thecarrier frequencies (or UL CCs) of UL resources may be indicated bysystem information. A cell operating in a primary frequency resource (ora PCC) may be referred to as a PCell and a cell operating in a secondaryfrequency resource (an SCC) may be referred to as an SCell. The PCell isused for a UE to establish an initial connection or to re-establish aconnection. The PCell may be a cell indicated during handover. The SCellmay be configured after an RRC connection is established and used toprovide additional radio resources. Both a PCell and an SCell may becollectively referred to as serving cells. Accordingly, if CA has notbeen configured for a UE in RRC_CONNECTED state or the UE inRRC_CONNECTED state does not support CA, one serving cell including onlya PCell exists for the UE. On the other hand, if CA has been configuredfor a UE in RRC_CONNECTED state, one or more serving cells including aPCell and one or more SCells exist for the UE. For CA, a network may addone or more SCells to a PCell initially configured during connectionestablishment, for a UE after initial security activation is initiated.

The LTE-A system may support aggregation of a plurality of CCs (i.e.,carrier aggregation) and consider a method for transmitting ACK/NACK fora plurality of DL data (e.g., data transmitted through a PDSCH)transmitted through a plurality of CCs through only one specific CC(e.g., PCC). As described above, a CC except for a PCC may be referredto as an SCC and ACK/NACK for DL data may be referred to as “A/N”. Inaddition, the LTE-A system may support cross CC scheduling duringcarrier aggregation. In this case, one CC (e.g., scheduled CC) may bepre-configured so as to be DL/UL scheduled through one specific CC(e.g., scheduling CC) (i.e., so as to receive DL/UL grant PDCCH forcorresponding scheduled CC). Cross CC scheduling (in terms of a UE) maybe an appropriate operation when a control channel region of an SCC isnot appropriate for PDCCH transmission due to interference influence, achannel state, etc.

If cross-carrier scheduling (or cross-CC scheduling) is used, a DLassignment PDCCH may be transmitted in DL CC #0 and a PDSCH associatedwith the PDCCH may be transmitted in DL CC #2. For cross-CC scheduling,a Carrier Indicator Field (CIF) may be introduced. The existence orabsence of a CIF in a PDCCH may be determined semi-statically andUE-specifically (or UE group-specifically) by higher-layer signaling(e.g. RRC signaling). The baseline of PDCCH transmission is summarizedas follows.

-   -   CIF disabled: a PDCCH in a DL CC allocates PDSCH resources of        the same DL CC or PUSCH resources of one linked UL CC.    -   CIF enabled: a PDCCH in a DL CC may allocate PDSCH resources or        PUSCH resources of a specific DL/UL CC from among a plurality of        aggregated DL/UL CCs using a CIF.

In the presence of a CIF, an eNB may allocate a PDCCH monitoring DL CCset to a UE in order to reduce blind decoding complexity of the UE. ThePDCCH monitoring CC set is a part of total aggregated DL CCs, includingone or more DL CCs. The UE detects/decodes a PDCCH only in the DL CCs ofthe PDCCH monitoring DL CC set. The PDCCH monitoring DL CC set may beconfigured UE-specifically, UE group-specifically, or cell-specifically.The term “PDCCH monitoring DL CC” may be replaced with an equivalentterm such as monitoring carrier, monitoring cell, etc. In addition, theterm CCs aggregated for a UE may be interchangeably used with anequivalent term such as serving CCs, serving carriers, serving cells,etc.

FIG. 13 illustrates an exemplary scheduling, when a plurality ofcarriers are aggregated. It is assumed that three DL CCs are aggregatedand DL CC A is set as a PDCCH monitoring DL CC. DL CCs A, B, and C maybe referred to as serving CCs, serving carriers, serving cells, etc. Ifa CIF is disabled, each DL CC may deliver only a PDCCH that schedules aPDSCH in the DL CC, without a CIF according to an LTE PDCCH rule. On theother hand, if a CIF is enabled by UE-specific (UE group-specific orcell-specific) higher-layer signaling, DL CC A (i.e. the monitoring CC)may deliver a PDCCH that schedules a PDSCH of another CC as well as aPDCCH that schedules a PDSCH of DL CC A, using the CIF. In this case, noPDCCH is transmitted in DL CCs B and C that are not set as PDCCHmonitoring DL CCs.

The LTE-A system considers transmission of a plurality of pieces ofACK/NACK information/a plurality of ACK/NACK signals in a specific ULCC, for a plurality of PDSCHs transmitted in a plurality of DL CCs. Forthis purpose, unlike ACK/NACK transmission using PUCCH format 1a/1b inthe legacy LTE, the plurality of ACK/NACK signals may be jointly encoded(e.g. using a reed-Muller code, a tail-biting convolutional code, etc.)and then the jointly encoded ACK/NACK information/signal may betransmitted in PUCCH format 2 or a new PUCCH format (referred to asPUCCH format 3). PUCCH format 3 includes the following blockspreading-based PUCCH format. For example, PUCCH format 3 may be used intransmitting an ACK/NACK, CSI (e.g. a CQI, a PMI, an RI, a PTI, etc.),and an SR alone or in combination.

FIG. 14 illustrates exemplary PUCCH format 3 at a slot level. In PUCCHformat 3, one symbol sequence is transmitted in the frequency domain andUEs are multiplexed using by time-domain spreading using OrthogonalCover Codes (OCCs). That is, the symbol sequence is spread with an OCCin the time domain. Control signals of a plurality of UEs may bemultiplexed into the same RB using OCCs.

Referring to FIG. 14, five SC-FDMA symbols (i.e. a UCI data part) aregenerated from one symbol sequence {d1, d2, . . . } using a length-5 OCCwith spreading factor (SF)=5, C1 to C5. The symbol sequence {d1, d2,}may be a modulation symbol sequence or a codeword bit sequence. If thesymbol sequence {d1, d2, . . . } is a codeword bit sequence, amodulation block is further included in the block diagram of FIG. 14.While two RS symbols (i.e. an RS part) are transmitted in one slot inFIG. 14, many other applications may be contemplated, including using anRS part with three RS symbols and a UCI data part configured with an OCCwith SF=4. The RS symbols may be generated by cyclically shifting aCAZAC sequence by a predetermined CS value. In addition, a plurality oftime-domain RS symbols may be multiplied by a specific OSS and thentransmitted. Block-spread UCI is transmitted to a network after it issubject to Fast Fourier Transform (FFT) and Inverse Fast FourierTransform (IFFT) on an SC-FDMA symbol basis. That is, theblock-spreading scheme modulates the control information (e.g. anACK/NACK, etc.) in SC-FDMA, as compared to the legacy PUCCH format 1 or2 series.

FIG. 15 illustrates exemplary PUCCH format 3 at a subframe level.

Referring to FIG. 15, a symbol sequence {d′0 to d′11} is mapped tosubcarriers of an SC-FDMA symbol and mapped to five SC-FDMA symbols byblock spreading using an OCC C1 to C5 in slot 0. Similarly, a symbolsequence {d′12 to d′23} is mapped to subcarriers of an SC-FDMA symboland mapped to five SC-FDMA symbols by block spreading using the OCC C1to C5 in slot 1. The symbol sequence of each slot, {d′0 to d′11} or{d′12 to d′23} is obtained by FFT-processing or FFT/IFFT-processing thesymbol sequence {d1, d2, . . . } illustrated in FIG. 15. If the symbolsequence {d′0 to d′11} or {d′12 to d′23} results from FFT-processing ofthe symbol sequence {d1, d2, . . . } illustrated in FIG. 15, the symbolsequence {d′0 to d′11} or {d′12 to d′23} is additionally IFFT-processedto generate SC-FDMA symbols. The total symbol sequence {d′0 to d′23} isgenerated by jointly encoding one or more pieces of UCI. The former halfof the symbol sequence {d′0 to d′23} is transmitted in slot 0 and thelatter half of the symbol sequence {d′0 to d′23} is transmitted in slot1. While not shown, different OCCs may be used in different slots andUCI data may be scrambled on an SC-FDMA symbol basis.

A resource for PUCCH format 3 may be explicitly given. In detail, aPUCCH resource set may be configured by a higher layer (e.g., RRC) and aPUCCH resource to be actually used may be indicated using an ACK/NACKresource indicator (ARI) value of a PDCCH.

FIG. 9 shows an example in which a PUCCH resource for HARQ-ACK isexplicitly indicated.

TABLE 9 HARG-ACK resource indicator (ARI) for PUCCH n_(PUCCH) 00 FirstPUCCH resource value configured by higher layer 01 Second PUCCH resourcevalue configured by higher layer 10 Third PUCCH resource valueconfigured by higher layer 11 Fourth PUCCH resource value configured byhigher layer.

In Table 9 above, a higher layer includes an RRC layer and an ARI valuemay be indicated through a PDCCH for carrying DL grant. For example, theARI value may be indicated using a transmit power control (TPC) field ofa SCell PDCCH and/or a PCell PDCCH that does not correspond to aninitial value of DAI.

FIG. 16 is a diagram illustrating an example in which a DL physicalchannel is allocated to a subframe.

Referring to FIG. 16, a PDCCH (for convenience, legacy PDCCH or L-PDCCH)used in the LTE(-A) system may be allocated to a control region of asubframe. In FIG. 16, an L-PDCCH region refers to a region to which thelegacy PDCCH is allocated. In the context, the L-PDCCH region may referto a control region, a control channel resource region (i.e., a CCEresource) to which a PDCCH can be actually allocated, or a PDCCH searchspace. A PDCCH may be additionally allocated in a data region (e.g., aresource region for a PDSCH, refer to FIG. 5). The PDCCH allocated tothe data region is referred to as an E-PDCCH. As illustrated in FIG. 16,a channel resource may be additionally ensured through the E-PDCCH toalleviate scheduling restrictions due to limited control channelresource of an L-PDCCH region.

In detail, the E-PDCCH may be detected/demodulated based on a DM-RS. TheE-PDCCH may be configured to be transmitted over a PRB pair on the timeaxis. In more detail, a search space (SS) for E-PDCCH detection may beconfigured with one or more (e.g., 2) E-PDCCH candidate sets. EachE-PDCCH set may occupy a plurality of (e.g., 2, 4, or 8) PRB pairs. Anenhanced-CCE (E-CCE) constituting an E-PDCCH set may be mapped in thelocalized or distributed form (according to whether one E-CCE isdistributed in a plurality of PRB pairs). In addition, when E-PDCCHbased scheduling is configured, a subframe for transmission/detection ofan E-PDCCH may be determined. The E-PDCCH may be configured in only aUSS. The UE may attempt DCI detection only on an L-PDCCH CSS and anE-PDCCH USS in a subframe (hereinafter, an E-PDCCH subframe) in whichE-PDCCH transmission/detection is configured and attempt DCI detectionon an L-PDCCH CSS and an L-PDCCH USS in a subframe (non-E-PDCCHsubframe) in which transmission/detection of E-PDCCH is not configured.

In the case of the E-PDCCH, in terms of one UE, a USS may include KE-PDCCH set(s) (for each CC/for each cell). K may be greater than orequal to 1 and equal to or smaller than a specific upper limit (e.g.,2). In addition, each E-PDCCH set (within a PDSCH region) may beconfigured with N PRBs. Here, N and PRB resource/index configured withthe N PRBs may be independently (i.e., set-specifically) allocated foreach respective E-PDCCH set. Accordingly, the number and index of E-CCEresources configured with each E-PDCCH set may be configured(UE-specially and) set-specifically. A PUCCH resource/index linked toeach E-CCE resource/index may also be allocated (UE-specifically and)set-specifically by independently configuration a start PUCCHresource/index for each respective E-PDCCH set. Here, the E-CCE mayrefer to a basic control channel unit of an E-PDCCH including aplurality of REs (within a PRB in a PDSCH region). The E-CCE may havedifferent structures according to an E-PDCCH transmission form. Forexample, an E-CCE for localized transmission may be configured using anRE belonging in the same PRB pair. On the other hand, an E-CCE fordistributed transmission may be configured with an RE extracted from aplurality of PRB pairs. In the case of the localized E-CCE, in order toperform optimum beamforming on each user, an antenna port (AP) may beindependently used for each respective E-CCE resource/index. On theother hand, in the case of distributed E-CCE, the same antenna port setmay be repeatedly used in different E-CCEs such that a plurality ofusers may commonly use antenna ports. The E-CCE may be referred to as aneCCE.

Like an L-PDCCH, an E-PDCCH carriers DCI. For example, the E-PDCCH maycarry DL scheduling information and UL scheduling information. AnE-PDCCH/PDSCH procedure and an E-PDCCH/PUSCH procedure are thesame/similar to in steps S107 and S108 of FIG. 1. That is, a UE mayreceive the E-PDCCH and receive data/control information through a PDSCHcorresponding to the E-PDCCH. In addition, the UE may receive theE-PDCCH and transmit data/control information through a PUSCHcorresponding to the E-PDCCH. The LTE(-A) system pre-reserves a PDCCHcandidate region (hereinafter, a PDCCH search space) in a control regionand transmits a PDCCH of a specific UE to a partial region of the PDCCHcandidate region. Accordingly, the UE may acquire a PDCCH of the UE inthe PDCCH search space via blind decoding. Similarly, the E-PDCCH may betransmitted over a partial or entire portion of a pre-reserved resource.

FIG. 17 illustrates resource allocation for an E-PDCCH and an E-PDCCHreceiving procedure.

Referring to FIG. 17, a BS transmits E-PDCCH resource allocation (RA)information to a UE (S1710). The E-PDCCH RA information may include RB(or virtual resource block (VRB)) allocation information. The RBallocation information may be given in units of RB or resource blockgroup (RBG). The RBG includes two or more consecutive RBs. The E-PDCCHRA information may be transmitted using higher layer (e.g., radioresource control layer and RRC layer) signaling. Here, The E-PDCCH RAinformation may be used to pre-reserve an E-PDCCH resource (region).Then the BS transmits an E-PDCCH to the UE (S1720). The E-PDCCH may betransmitted in a partial region or an entire region of the E-PDCCHresource (e.g., M RBs) that is reserved in step S1710. Accordingly, theUE may monitor a resource (region) (hereinafter, E-PDCCH search space)in which an E-PDCCH can be transmitted (S1730). The E-PDCCH search spacemay be given as a portion of the RB set allocated in step S1710. Here,the monitoring includes blind decoding or blind detection of a pluralityof E-PDCCH candidates in the E-PDCCH search space.

The LTE-A system (a system according to 3GPP technology standard (TS) 36series Release 9, 10) has introduced a PUCCH transmit diversity (TxD)transmission scheme such as spatial orthogonal resource transmitdiversity (SORTD), etc. in order to enhance UL control information (UCI)based on PUCCH (e.g., to ensure UL coverage). In the case of SORTD, thesame UCI information may be simultaneously transmitted through differentPUCCH resources allocated to a plurality of (e.g., 2) antennas. Forexample, when ACK/NACK is transmitted through two antennas based onSORTD, two PUCCH resources for ACK/NACK transmission may be required. Afirst PUCCH resource of the two PUCCH resources may be determined as animplicit PUCCH resource linked to a lowest CCE index n_CCE constitutinga DL grant PDCCH for scheduling DL data corresponding to ACK/NACK (referto Equation 1) and a second PUCCH resource may be determined as animplicit PUCCH resource linked to a CCE index n_CCE+1 immediately afterthe lowest CCE index. For convenience, a PUCCH resource for transmissionof ACK/NACK may be referred to as an ACK/NACK resource. Although twoantennas are exemplified, the same principle may also be applied to thecase in which three or more antennas are used.

As described above, the LTE-A system supports aggregation for aplurality of CCS/cells (i.e., carrier aggregation) for improving datathroughput. In the case of carrier aggregation, an ACK/NACK transmissionscheme such as a channel selection method may be used to feedback aplurality of ACK/NACKs for a plurality of DL data transmitted through aplurality of CCs/cells. As described above, in the channel selectionmethod, a plurality of PUCCH resources for a plurality of CCs/cells (aplurality of transport block (TB) transmitted through the CCs/cells) isallocated and a combination of different PUCCH resources and/or QPSKmodulation symbols may be selected/transmitted according to an ACK/NACKstate. For example, in the case of CC/cell configured to transmit up totwo TBs, two PUCCH resources may be allocated in order to ensure aplurality of PUCCH resources for channel selection. A first PUCCHresources of the two PUCCH resources may be determined as an implicitPUCCH resource linked to a lowest CCE index n_CCE constituting a DLgrant PDCCH for scheduling DL data (refer to Equation 1) and a secondPUCCH resource may be determined as an implicit PUCCH resource linked toan index n_CCE+1 immediately after the lowest CCE index. Althoughtransmission of ACK/NACK for two DL data is exemplified, the sameprinciple may also be applied to the case of transmission of ACK/NACKfor three or more DL data.

FIG. 18 illustrates an example for determining a PUCCH resource in thecase of the SORTD method or the channel selection method.

Referring to FIG. 18, a UE may monitor DL grant PDCCH and detect DLgrant PDCCH from CCE indexes 4 to 7. In this case, a lowest CCE indexconstituting DL grant PDCCH is 4 and the DL grant PDCCH is configuredwith four CCEs (e.g., CCE indexes 4 to 7), and thus a CCE aggregationlevel may be 4. Accordingly, two PUCCH resources for the SORTD method orthe channel selection method may be determined as a PUCCH resource(e.g., PUCCH resource 4) linked to a lowest CCE index (e.g., CCE index4) and a PUCCH resource (e.g., PUCCH resource 5) linked to a CCE index(e.g., CCE index 5) immediately after the lowest CCE index.

As described above, the LTE-A system (e.g. a system according to 3GPP TS36 series Release 10) may introduce a scheduling method using an E-PDCCHfor providing more improved/effective control signaling. The schedulingmethod using the E-PDCCH may refer to a method for transmitting controlinformation (e.g., PDCCH) through data (e.g., PDCCH) region. The E-PDCCHmay be configured/transmitted based on an eCCE (or an E-CCE) that is abasic control unit corresponding to the concept of a CCE constituting anL-PDCCH. In addition, similarly to the legacy system, linkage betweeneCCE resource/index and PUCCH resource/index may also be pre-configuredfor a PUCCH resource for transmission of ACK/NACK for DL data scheduledby the DL grant E-PDCCH. Alternatively, a parameter (e.g., a start pointof PUCCH resource/index linked to eCCE resource/index) for inferringlinkage between eCCE resource/index and PUCCH resource/index may bepre-configured. Based on this, an ACK/NACK resource for DL data may bedetermined as an implicit PUCCH resource linked to a specific (e.g.,lowest) eCCE index constituting an E-PDCCH for scheduling DL data.Hereinafter, the lowest eCCE index constituting an E-PDCCH may bereferred to as n_eCCE.

In the case of E-PDCCH, a second ACK/NACK resource for applying feedbackof a plurality of ACK/NACKs based on channel selection and ACK/NACKtransmit diversity (TxD) based on SORTD may be determined as an implicitPUCCH resource linked to an eCCE index n_eCCE+1 immediately after thelowest eCCE index constituting an E-PDCCH. However, when an eCCEaggregation level is 1, the eCCE index n_eCCE+1 immediately after thelowest eCCE index may be used to configure another E-PDCCH, therebycausing collision in a PUCCH resource linked to the eCCE index n_eCCE+1.Likewise, when the legacy method is used, resource blocking may occurand E-PDCCH scheduling may be limited.

FIG. 19 illustrates resource blocking. In an example of FIG. 19, it isassumed that an ACK/NACK signal is fed back using two ACK/NACKs via theSORTD method or the channel selection method.

Referring to FIG. 19, a first E-PDCCH is configured with one eCCE withan eCCE index 4. A second E-PDCCH may be configured with one eCCE withan eCCE index 5. In this case, a first PUCCH resource for the firstE-PDCCH may be determined as a PUCCH resource (e.g., PUCCH resource 4)linked to a lowest eCCE index constituting the first E-PDCCH and asecond PUCCH resource for the first E-PDCCH may be determined as a PUCCHresource (e.g., PUCCH resource 5) liked to an index immediately afterthe lowest eCCE index. On the other hand, a first PUCCH resource for thesecond E-PDCCH may be determined as a PUCCH resource (e.g., PUCCHresource 5) linked with a lowest eCCE index constituting the secondE-PDCCH. Thus collision may be caused in PUCCH resource 5, and thus a BScannot configure the second E-PDCCH using eCCE index 5 duringscheduling. That is, eCCE index 5 cannot be used to configure anotherE-PDCCH and is blocked, thereby limiting scheduling.

In this case, assuming that a UE accurately knows the number of eCCEresources constituting DL grant E-PDCCH scheduled to the UE, it may bepossible to more appropriately and flexibly allocate a PUCCH resource(e.g., a second ACK/NACK resource) according to a size of an eCCEaggregation level (e.g., according to whether an eCCE aggregation levelis 1 or an eCCE aggregation level is equal to or greater than 1). Inaddition, when the UE can recognize eCCE resource/index informationcontained in a PDSCH receiving region scheduled/allocated to the UEthrough DL grant E-PDCCH, it may be more preferable to use an implicitPUCCH resource linked to eCCE resource/index contained in the PDSCHreceiving region as a PUCCH resource (e.g., a second ACK/NACK resource)in terms of PUCCH resource usage efficiency and scheduling flexibility.

Accordingly, the present invention proposes an effective ACK/NACKtransmit resource allocation method appropriate for E-PDCCH-based DLdata scheduling. In detail, the present invention proposes a method forallocating a plurality of ACK/NACK resources using a configuring methodof a search space for E-PDCCH detection in consideration of SORTD-basedACK/NACK transmit diversity (TxD) transmission and channelselection-based feedback of a plurality of ACK/NACKs. In detail, in themethod according to the present invention, a PUCCH resource linked toeach resource index contained in the E-PDCCH and the PDSCH may beallocated to a plurality of ACK/NACK resources.

Hereinafter, a search space for E-PDCCH detection may be referred to asan E-SS. In addition, the number of eCCE resources constituting DL grantE-PDCCH may be referred to as an eCCE aggregation level. In addition,“eCCE contained in a scheduled PDSCH region” may refer to the case inwhich even some of REs constituting an eCCE are contained in the PDSCHregion or the case in which all of the REs constituting the eCCE arecontained in the PDSCH region. In addition, linkage between a PRB indexand PUCCH resource/index is pre-configured or a parameter (e.g., a startpoint of PUCCH resource/index linked to PRB index) for inferring thelinkage between the PRB index and the PUCCH resource/index ispre-configured, “eCCE constituting DL grant E-PDCCH” or “eCCE includedin scheduled PDSCH region” may be replaced with “PRB constituting DLgrant E-PDCCH” and “PRB contained in scheduled PDSCH region”,respectively. In this case, the PRB may also refer to the case in whicheven some of REs constituting a PRB are contained in the E-PDCCH orPDSCH region or the case in which all of the REs constituting the PRBare contained in the E-PDCCH or PDSCH region. Hereinafter, when anACK/NACK resource is inferred (or determined) based on a PRB index, theACK/NACK resource allocating method according to the present inventioncan be applied irrespective of whether entire E-CCE resource/indexinformation is applied.

When Entire E-CCE Resource/Index Information (Whole eCCE Map) isProvided

Entire eCCE resource/index assignment information in an entire PDSCHregion may be provided to a UE. For convenience, the eCCE resource/indexassignment information may be referred to as an eCCE map. In addition,E-SS resource information for E-PDCCH detection for a specific UE basedon an eCCE map may be provided to the specific UE. Accordingly, the UEmay recognize eCCE resource/index constituting E-SS based on the eCCEmap. In this case, the entire eCCE map and E-SS resource information forthe specific UE may be provided via higher layer signaling (e.g., RRCsignaling, etc.).

Method 1-1

When eCCE resource/index for E-SS is known, two ACK/NACK resources maybe determined as an implicit PUCCH resource linked to a specific (e.g.,lowest) eCCE index constituting DL grant E-PDCCH and an implicit PUCCHresource linked to a specific (e.g., lowest) eCCE index contained in aPDSCH region scheduled by an E-PDCCH. In the method according to thepresent invention, a PUCCH linked to an eCCE index used by anE-PDCCH/PDSCH pair is allocated to an ACK/NACK resource, and thus eCCEblocking may be prevented irrespective of a size of an eCCE aggregationlevel.

FIG. 20 illustrates a method for determining two PUCCH resourcesaccording to the present invention. In an example of FIG. 20, it isassumed that an eCCE is consecutively allocated in a localized resourceallocation method. However, when a distributed resource allocationmethod is applied, the same principle of FIG. 20 may also be applied.

Referring to FIG. 20, an eCCE index constituting DL grant E-PDCCH is 4and 5, a lowest eCCE index is 4. Accordingly, an index of an implicitPUCCH resource linked to a lowest eCCE index constituting DL grantE-PDCCH is 4. In addition, an eCCE index of a PDSCH scheduled by anE-PDCCH is 12 to 15, and thus a lowest eCCE index contained in a PDSCHregion is 12. Accordingly, an index of an implicit PUCCH resource linkedto a lowest eCCE index contained in a PDSCH region scheduled by anE-PDCCH is 12.

In an example of FIG. 20, since an E-PDCCH is configured with two eCCEs(e.g., 4 and 5), when a conventional method is used, two ACK/NACKresources may be determined as a PUCCH resource 4 linked to a lowesteCCE index constituting the E-PDCCH and a PUCCH resource 5 after thePUCCH resource 4. Thus when two aggregation levels are used, eCCEblocking may not occur. However, assuming that an E-PDCCH is configuredwith one eCCE, blocking may occur in an eCCE index 5 in the conventionalmethod. On the other hand, even if an E-PDCCH is configured one eCCE,blocking does not occur in an eCCE index 5 in the method according tothe present invention.

The example of FIG. 20 is merely an example, and another eCCE index anda PUCCH index, and linkage therebetween may be used. In addition,although the case in which a specific eCCE index is determined as aPUCCH resource linked to a lowest eCCE index has been exemplified, thespecific eCCE index may be determined using another method.

Method 1-2

Unlike in Method 1-1, other information instead of a specific eCCE indexconstituting DL grant E-PDCCH may be used. Two ACK/NACK resources may bedetermined as two implicit PUCCH resources linked to two specific (e.g.,lowest) eCCE indexes contained in a scheduled PDSCH region. For example,two ACK/NACK resources may be determined as an implicit PUCCH resourcelinked to a lowest eCCE index contained in a PDSCH region and animplicit PUCCH resource linked to a second lowest eCCE index containedin the PDSCH region. Similarly, in the method according to the presentinvention, a PUCCH resource linked to an eCCE index used by a PDSCH isallocated as an ACK/NACK resource, and thus eCCE blocking may beprevented irrespective of a size of an eCCE aggregation level.

FIG. 21 illustrates a method for determining two PUCCH resourcesaccording to the present invention. In an example of FIG. 21, an E-PDCCHand a PDSCH may be configured from different resource blocks (RBs)according to a distribute resource allocation method. For example,assuming four eCCEs constitute one RB, the E-PDCCH may be configuredwith eCCE indexes 4 and 16 and the PDSCH may be configured with eCCEindexes 0, 8, 12, and 17 in the example of FIG. 21. The resourceallocation of FIG. 21 is merely an example and the same principle ofFIG. 21 may also be applied to resource allocating using another method.

Referring to FIG. 21, an eCCE index contained in a PDSCH regionscheduled by an E-PDCCH is 0, 8, 12, and 17, and thus a lowest eCCEindex contained in the PDSCH region is 0 and a second lowest eCCE indexis 8. Thus, when Method 1-2 is sued, two PUCCH resources may bedetermined as PUCCH resources (e.g., PUCCH indexes 0 and 8) linked toeCCE indexes 0 and 8. In addition, when Method 1-1 is used, a lowesteCCE index constituting an E-PDCCH is 4 and a lowest eCCE indexcontained in the PDSCH is 0, and thus two ACK/NACK resources may bedetermined as a PUCCH resource (e.g., PUCCH index 4) linked with alowest eCCE index constituting an E-PDCCH and a PUCCH resource (e.g.,PUCCH index 0) linked to a lowest eCCE index contained in a PDSCH.

On the other hand, when the conventional method is used, since a lowesteCCE index constituting an E-PDCCH is 4, two ACK/NACK resources may bedetermined as a PUCCH resource 4 linked to a lowest eCCE indexconstituting an E-PDCCH and PUCCH resource 5 linked to a second lowesteCCE index. In the conventional method, blocking may occur in eCCE index5, but blocking may be prevented in the methods according to the presentinvention.

In Method 1-2, when PRB index-based ACK/NACK resource allocation isapplied, only one PRB (PRB index n_PRB) may be allocated to a PDSCH. Inthis case, an implicit PUCCH resource linked to n_PRB is determined as afirst ACK/NACK resource and an implicit PUCCH resource linked to a PRBindex n_PRB+1 is determined as a second ACK/NACK resource, or anexplicit PUCCH resource that is separately allocated via higher layersignaling (e.g., RRC signaling) may be determined as a second ACK/NACKresource.

Method 1-3

As another method, two ACK/NACK resources may be determined as twoimplicit PUCCH resources linked to two specific (e.g., lowest) eCCEindexes of all eCCEs including eCCEs constituting DL grant E-PDCCH andeCCEs contained in a PDSCH region (scheduled by an E-PDCCH). Forexample, two ACK/NACK resources may be determined as an implicit PUCCHresource linked to a lowest eCCE index of all eCCEs and an implicitPUCCH resource linked to a second lowest eCCE index of all eCCEs. Method1-3 can be advantageously applied to the case in which a UE canaccurately know an eCCE aggregation level of DL grant E-PDCCH.

FIG. 22 illustrates an example for determining two PUCCH resourcesaccording to the present invention. In an example of FIG. 22, the samesituation as in FIG. 21 is assumed. However, the same principle of FIG.22 can also be applied to a different resource allocation method from adistributed resource allocation method.

Referring to FIG. 22, an eCCE index constituting an E-PDCCH is 4 and 16and an eCCE index contained in a PDSCH region scheduled by an E-PDCCH is0, 8, 12, and 17, and thus all eCCEs are 0, 4, 8, 12, 16, and 17. Thus,a lowest eCCE index of all eCCEs is 0 and a second lowest eCCE index ofthe all eCCEs is 4. Accordingly, when Method 1-3 is used, two ACK/NACKresources may be determined as a PUCCH resource (e.g., PUCCH index 0)linked to a lowest eCCE index of the all eCCEs and a PUCCH resource(e.g., PUCCH index 4) linked to a second lowest eCCE index of the alleCCEs. Accordingly, in Method 1-3, blocking may also be preventedirrespective of an eCCE aggregation level.

Method 1-4

Since a UE can know an eCCE aggregation level in Method 1-3, Method 1-3can be modified so as to apply different methods according to eCCEaggregation levels. When an eCCE aggregation level is 1, Methods 1-1 to1-3 can be applied in order to prevent resource blocking. When an eCCEaggregation level is greater than 1, DL grant E-PDCCH may be configuredwith two or more eCCEs. Accordingly, when the number of ACK/NACKresources is smaller than an eCCE aggregation level, even if a pluralityof PUCCH resources linked to an eCCE index constituting an E-PDCCH isdetermined as ACK/NACK resources, resource blocking can be prevented.Thus, when an eCCE aggregation level is greater than 1, two implicitPUCCHs linked to two specific (e.g., lowest) eCCE indexes constitutingDL grant E-PDCCH may be determined as two ACK/NACK resources.

For example, when an eCCE aggregation level is 1, two ACK/NACK resourcesmay be determined using Methods 1-1 to 1-3. On the other hand, when aneCCE aggregation level is greater than 1, for example, referring back toFIG. 22, two ACK/NACK resources may be determined as implicit PUCCHresources linked to eCCE index 4 and eCCE index 16 constituting DL grantE-PDCCH.

A method to be selected/applied among Methods 1-1 to 1-4 may beexplicitly signaled via higher layer signaling (e.g., RRC signaling),PDCCH/E-PDCCH, etc. or implicitly determined according to specificinformation associated with transmission of E-PDCCH/PDSCH. For example,the specific information associated with the transmission ofE-PDCCH/PDSCH may include an antenna port, scrambling ID, and number oflayers.

When a PRB that does not include an eCCE is present in an eCCE map, thecurrent case is considered as a case in which only E-SS resourceinformation is provided, and an ACK/NACK resource allocation method maybe applied, as described below. The case in which the PRB that does notinclude an eCCE is present in the eCCE map may be the case in which thePRB does not include all REs constituting an eCCE or the case in whichthe PRB includes only some of REs constituting the eCCE.

When Entire E-CCE Resource/Index Information (Whole eCCE Map) is notProvided

So far, it has been assumed that entire eCCE resource/index assignmentinformation and E-SS resource information for E-PDCCH detection for aspecific UE are provided. However, the entire eCCE resource/indexassignment information may not be provided and only E-SS resourceinformation may be provided to the UE. The E-SS resource information forE-PDCCH detection may be provided to the UE via, for example, higherlayer signaling (e.g., RRC signaling), etc. When only the E-SS resourcedinformation without the entire eCCE resource/index assignmentinformation is provided, the UE cannot accurately know whether an eCCEcontained in a PDSCH region scheduled by DL grant E-PDCCH is present.Accordingly, the above methods can be modified as follows.

Method 2-1

According to whether an eCCE contained in a PDSCH scheduled by DL grantE-PDCCH on E-SS is present, an ACK/NACK resource allocation method maybe varied. First, when the eCCE contained in the scheduled PDSCH regionis present on E-SS, eCCE resource/index assignment information isprovided, and thus an ACK/NACK resource allocation method can be appliedin the same way as in the case in which entire eCCE resource/indexassignment information is applied. When the eCCE contained in thescheduled PDSCH region is present on E-SS, for example, Methods 1-1 to1-4 may be applied.

Method 2-2

On the other hand, when the eCCE contained in the scheduled PDSCH regionis not present on E-SS, a specific eCCE index contained in the PDSCHregion cannot be used. Thus, in this case, an implicit PUCCH resourcelinked to a specific (e.g., lowest) eCCE index n eCCE constituting DLgrant E-PDCCH for scheduling a PDSCH may be determined as a firstACK/NACK resource, and an implicit PUCCH resource linked to an indexn_eCCE+1 immediately after the specific eCCE index constituting the DLgrant E-PDCCH or an explicit PUCCH resource that is separately allocatedvia higher layer (e.g., RRC) may be determined as a second ACK/NACKresource.

Method 2-3

When a UE can accurately know an eCCE aggregation level of DL grantE-PDCCH, different ACK/NACK resource allocation methods may be appliedaccording to a size of eCCE aggregation level. When the eCCE aggregationlevel is 1, an implicit PUCCH resource linked to n_eCCE+1 or an explicitPUCCH resource based on a higher layer (e.g., RRC) may be determined asa second ACK/NACK resource. When the eCCE aggregation level is greaterthan 1, two implicit PUCCH resources linked to two specific (e.g.,lowest) eCCE indexes constituting DL grant E-PDCCH may be determined astwo ACK/NACK resources similarly to Method 1-4.

A method to be selected/applied among Methods 2-1 to 2-3 may beexplicitly signaled via higher layer signaling (e.g., RRC signaling),PDCCH/E-PDCCH, etc. or implicitly determined according to specificinformation associated with transmission of E-PDCCH/PDSCH. For example,the specific information associated with the transmission ofE-PDCCH/PDSCH may include an antenna port, scrambling ID, and number oflayers.

When DL Grant is Received Through an L-PDCCH

So far, the present invention has been described in terms of an E-PDCCHand an eCCE, the present invention is not limited only to the case ofE-PDCCH. For example, E-SS resource information and/or eCCE mapinformation may be provided and DL grant for PDSCH scheduling may betransmitted through an L-PDCCH instead of an E-PDCCH. In this case,similarly to Method 1-1, an ACK/NACK resource may be determined. Forexample, an implicit PUCCH resource linked to a lowest CCE index n_CCEconstituting an L-PDCCH may be determined as a first ACK/NACK resourceand an implicit PUCCH resource linked to a specific (e.g., lowest) eCCEindex contained in a PDSCH region scheduled by an L-PDCCH may bedetermined as a second ACK/NACK resource.

Alternatively, when an eCCE contained in a scheduled PDSCH region is notpresent, an ACK/NACK resource may be determined similarly to Method 2-2.For example, an implicit PUCCH resource linked to an index n_CCE+1immediately after a lowest CCE index constituting an L-PDCCH or anexplicit PUCCH resource based on higher layer (e.g., RRC) may bedetermined as a second ACK/NACK resource.

As another method, an ACK/NACK resource may be determined similarly toMethod 1-2. For example, two implicit PUCCH resources linked to twospecific (e.g., lowest) eCCE indexes contained in a scheduled PDSCHregion without CCE information of DL grant L-PDCCH may be determined astwo ACK/NACK resources. In this case, when PRB index-based ACK/NACKresource allocation is applied and only one PRB (index n_PRB) isallocated to a PDSCH, an implicit PUCCH resource linked to n_PRB may bedetermined as a first ACK/NACK resource and an implicit PUCCH resourcelinked to an index n_PRB+1 or an explicit PUCCH resource that isseparately allocated via higher layer (e.g., RRC) may be determined as asecond ACK/NACK resource.

In addition, it may be possible to consider an L-PDCCH as an E-PDCCH andto determine an ACK/NACK resource using Methods 1-3, 1-4, 2-1, and 2-3.

A method to be selected/applied may be explicitly signaled via higherlayer signaling (e.g., RRC signaling), PDCCH/E-PDCCH, etc. or implicitlydetermined according to specific information associated withtransmission of PDCCH/PDSCH. For example, the specific informationassociated with the transmission of PDCCH/PDSCH may include an antennaport, scrambling ID, and number of layers.

PDSCH Received without DL Grant PDCCH (PDSCH without PDCCH)

E-SS resource information and/or an eCCE map may be provided and a PDSCHwithout DL grant PDCCH (PDSCH without PDCCH) may be received. Forexample, a BS may schedule PDSCH transmission via semi-persistentscheduling (SPS) via a higher layer (e.g., RRC) and may not transmit aPDCCH whenever a PDSCH is transmitted. Accordingly, when a PDSCH isreceived without DL grant, two implicit PUCCH resources linked to twospecific (e.g., lowest) eCCE indexes contained in a region of a PDSCH(PDSCH without PDCCH) received without a PDCCH may be determined as twoACK/NACK resources similarly to Method 1-2.

However, an eCCE contained in a PDSCH region may not be present. In thiscase, unlike in Methods 2-1 to 2-3, an eCCE (or CCE) index of an E-PDCCH(or L-PDCCH) cannot be used. Accordingly, two explicit PUCCH resourcesallocated via a higher layer (e.g., RRC) may be determined as twoACK/NACK resources.

In this case, when PRB index-based ACK/NACK resource allocation isapplied and only one PRB (index n_PRB) is allocated to a correspondingPDSCH, an implicit PUCCH resource linked to n_PRB may also be determinedas a first ACK/NACK resource, and an implicit PUCCH resource linked toan index n_PRB+1 or an explicit PUCCH resource that is separatelyallocated via a higher layer (e.g., RRC) may also be determined as asecond ACK/NACK resource.

When only one ACK/NACK resource corresponding to a PDSCH (PDSCH withoutPDCCH) received without a PDCCH is required (e.g., when non-transmitdiversity (non-TxD)-based PUCCH transmit mode and/or a DL transmit modein which up to one transport block is possible are configured), oneimplicit PUCCH resource linked to a specific (e.g., lowest) eCCE indexcontained in a PDSCH region may be determined as an ACK/NACK resource.Alternatively, when an eCCE contained in a PDSCH region is not present,one explicit PUCCH resource allocated via a higher layer (e.g., RRC) maybe determined as an ACK/NACK resource.

PDCCH that does not Schedule PDSCH (PDCCH without PDSCH)

E-SS resource information and/or an eCCE map may be provided andACK/NACK feedback is required, but a PDCCH (PDCCH without PDSCH) thatdoes not schedule a PDSCH may be received. For example, a PDCCHindicating SPS configuration release may not schedule a PDSCH, but a UEmay transmit ACK/NACK for the PDCCH indicating SPS release. The PDCCHindicating SPS release may be received in the form of E-PDCCH. In thiscase, since an eCCE contained in a PDSCH region is not present, anACK/NACK resource may be determined using the same or similar method toMethod 2-2.

When ACK/NACK resource allocation is inferred based on only a PRB indexcontained in a scheduled PDSCH region, a PDSCH scheduled from a PDCCH(PDCCH without PDSCH) is not defined, and thus a PRB (index) containedin a PDSCH region and a PUCCH resource (index) linked thereto may notalso be present/inferred. Accordingly, the present invention proposes amethod for transmitting a PDCCH (PDCCH without PDSCH) that does notschedule a PDSCH using a legacy L-PDCCH method, but not the form ofE-PDCCH when E-PDCCH-based scheduling is configured to be applied.Accordingly, two ACK/NACK resources may be determined as an implicitPUCCH resource linked to a lowest CCE index n_CCE constituting a PDCCH(PDCCH without PDSCH) transmitted based on an L-PDCCH and an implicitPUCCH resource linked to a CCE index n_CCE+1 immediately after thelowest CCE index.

So far, for convenience of description, a method forallocating/determining two ACK/NACK resources (i.e., a first ACK/NACKresource and a second ACK/NACK resource) from one E-PDCCH/PDSCH pair, anL-PDCCH/PDSCH pair, or a PDSCH has been described. However, this ismerely an example and the present invention may also be applied in thesame way or similarly even when allocation of three or more ACK/NACKresources (or PUCCH resource) is required for specific reason/purpose,etc. For example, referring to FIG. 20, assuming that a UE canaccurately know an eCCE aggregation level of DL grant E-PDCCH, the totalnumber of E-PDCCHs and eCCEs resources/indexes contained in a PDSCHregion scheduled from the E-PDCCHs may be six. Accordingly, up to sixPUCCH resources (e.g., PUCCH indexes 4, 5, 12, 13, 14, and 15) can beused, and thus SORTD transmission through up to six antennas andACK/NACK transmission using up to six PUCCH resources may be possible.

When only one ACK/NACK resource is allocated to one E-PDCCH/PDSCH pairor L-PDCCH/PDSCH pair, one ACK/NACK transmission resource may also bedetermined as an implicit PUCCH resource linked to a specific CCE indexconstituting an L-PDCCH or a specific eCCE constituting an E-PDCCH or asan implicit PUCCH linked to a specific eCCE index contained in ascheduled PDSCH region. In this case, a method to be selected/appliedmay also be explicitly signaled via higher layer signaling (e.g., RRCsignaling), PDCCH/E-PDCCH, etc. or may also be implicitly determinedaccording to specific information associated with transmission of(E-)PDCCH/PDSCH. For example, the specific information associated withthe transmission of (E-)PDCCH/PDSCH may include an antenna port,scrambling ID, and number of layers.

Even if the aforementioned method for determining an ACK/NACK resource(one of Methods 1-1 to 1-4, Methods 2-1 to 2-3, the method for the casein which DL grant is received through an L-PDCCH, the method for a PDSCH(PDSCH without PDCCH) received without DL grant PDCCH, and the methodfor PDCCH (PDCCH without PDSCH) that does not schedule a PDSCH) isapplied, ACK/NACK resources may collide with each other betweendifferent users or different layers during MIMO transmission ofmulti-layer)/multi-user for E-PDCCH/PDSCH. In addition, an ACK/NACKresource linked to a CCE for an L-PDCCH and an ACK/NACK resource linkedto an eCCE for an E-PDCCH may collide with each other. Accordingly,according to the present invention, in order to prevent collisionbetween the ACK/NACK resources, “an implicit PUCCH resource/index nPUCCH linked to a specific (e.g., lowest) eCCE index n_eCCE” containedin DL grant E-PDCCH/PDSCH transmission region may be determined as “animplicit PUCCH resource linked to an eCCE index (n_eCCE+n_offset)obtained by adding a specific offset n_offset to a specific eCCE index neCCE” or “PUCCH resource/index (n_PUCCH+n_offset) obtained by adding aspecific offset n_offset to an implicit PUCCH resource/index n_PUCCHlinked to a specific eCCE index n_eCCE”. For convenience, the specificoffset n_offset may be referred to as “offset ACK/NACK resourceindicator (ARI)” or simply referred to as “ACK/NACK resource offset(ARO)”. The specific offset n_offset may be explicitly signaled viahigher layer (e.g., RRC), PDCCH/E-PDCCH, etc. or may be implicitlydetermined according to specific information associated withE-PDCCH/PDSCH transmission. For example, the specific informationassociated with E-PDCCH/PDSCH transmission may include an antenna port,scrambling ID, and number of layers.

Equation 2 shows a method for determining an ACK/NACK resource usingoffset ARI or ARO. When the offset ARI or ARO is added, Equation 1 maybe corrected to Equation 2.n _(PUCCH) ⁽¹⁾ =n _(CCE) +N _(PUCCH) ⁽¹⁾ +n_offset  [Equation 2]

In Equation 2, n⁽¹⁾ _(PUCCH) is a resource index indicating an ACK/NACKresource, N⁽¹⁾ _(PUCCH) is a value signaled via higher-layer signaling,n_(CCE) is the lowest index of eCCE indexes constituting an E-PDCCH, andn_offset indicates offset ARI or ARO. Equation 2 is a merely an example,and additional calculation may be performed on each parameter or otherparameters may be used in order to determine an ACK/NACK resource.

Table 10 below shows a method for signaling offset ARI (or ARO) throughDCI format. As described below, values shown in Table 10 may be signaledthrough an added field for ACK/NACK resource information in the DCIformat or offset ARI (or ARO) may be signaled using an existing field(e.g., a transmit power control (TPC) field) in the DCI format.

TABLE 10 field in DCI format n_offset 0 0 1 −1 2 −2 3 2.

In the case of the LTE-A system, a BS may configure a plurality ofexplicit PUCCH (e.g., format 1b or 3) resources (sets) through a higherlayer (e.g., RRC) and information indicating one resource (set) of theconfigured resources (sets) may be transmitted through a DL grant PDCCH(refer to Table 9). For convenience, the indicating information may bereferred to as “index ARI” or simply referred to as “ARI”. For example,the ARI may indicate one of four PUCCH resources. Index ARI may bereferred to as ACK/NACK resource index information.

A TPC field in the DCI format indicates a change amount of transmitpower for transmit power control. However, when a plurality of carriersis aggregated, a value indicating transmit power control may be receivedthrough a TPC field in the DCI format received through PCC/Pcell. Thatis, the legacy PUCCH transmit control method refers to a TPC command inDL grant PDCCH that schedules PCC/Pcell. Accordingly, a TPC field in theDCI format received through SCC/SCell may not be used for original use(transmit power control).

Accordingly, the specific offset (ARO or offset ARI) that is applied todetermine a first ACK/NACK resource and/or a second ACK/NACK resourcefor CC/cell based on the aforementioned ACK/NACK resource determiningmethod or other methods is explicitly signaled through DL grant E-PDCCH,a method (hereinafter, referred to as “add ARI field”) for adding a newfield (e.g., 2-bit field) for offset ARI signaling in DL grant DCIformat for signaling of offset ARI or a method (hereinafter, referred toas “reuse existing field”) for reusing an existing specific field (e.g.,a transmit power control (TPC) field) in DL grant DCI format may beconsidered. Accordingly, in order to maintain a legacy PUCCH transmitpower control method that refers to a TPC command in DL grant (E-)PDCCHfor scheduling PCC/Pcell and to simultaneously reduce control channeloverhead due to unnecessary increase in DCI format, the presentinvention proposes the following method for configuring and applying anARI field according to scheduling target CC/cell and PUCCH ACK/NACKtransmission mode, and whether cross-CC is scheduled. Offset ARI may bereferred to as ACK/NACK resource offset information, and a field to beadded in DCI format for signaling of offset ARI for ACK/NACK resourceinformation may be referred to as an ARI field.

Method 3

-   -   In the case of DL grant E-PDCCH for scheduling PCC/Pcell        -   ARI field configuration: add ARI field        -   ARI application method: offset ARI    -   In the case of DL grant E-PDCCH for scheduling SCC/Scell        -   when ACK/NACK transmission mode is configured in PUCCH            format 3            -   ARI field configuration: reuse existing field (e.g.,                reuse TPC field)            -   ARI application method: index ARI        -   When an ACK/NACK transmission mode is configured for channel            selection and cross-CC scheduling is configured            -   ARI field configuration: reuse existing field (e.g.,                reuse TPC field)            -   ARI application method: offset ARI        -   When an ACK/NACK transmission mode is configured for channel            selection and cross-CC scheduling is not configured            -   ARI field configuration: reuse existing field (e.g.,                reuse TPC field)            -   ARI application method: index ARI

FIG. 23 is a flowchart of a method for signaling ACK/NACK resourceinformation according to the present invention. In an example of FIG.23, it is assumed that a first carrier and a second carrier areaggregated for a UE. The first carrier may be PCC/Pcell and the secondcarrier may be SCC/Scell. As described with reference to FIG. 12, when aplurality of carriers is aggregated, the UE may transmit an ACK/NACKsignal through PCC/Pcell.

Referring to FIG. 23, the UE may receive DL control information (e.g.,DCI format) from a BS through DL grant E-PDCCH (step S2302). The DLcontrol information (e.g., DCI format) may include a field (e.g., TPCfield) for power transmission control information and a field forresource allocation information for scheduling a PDSCH. In addition, theDCI format may include ACK/NACK resource information (e.g., offset ARIor index ARI) for preventing collision of ACK/NACK resources.

In step S2304, the UE may receive DL data using resource allocationinformation received in step S2302. Then, in step S2306, the UE maytransmit the ACK/NACK signal for the DL data received in step S2304. TheACK/NACK signal may be transmitted through the first carrier and in thiscase, the first carrier may be PCC/Pcell.

When the E-PDCCH schedules the first carrier, DL data may be received inthe first carrier in step S2304. In this case, according to the presentinvention, a field for ACK/NACK resource information may be added in theDL control information (e.g., DCI format) received through an E-PDCCHand a field for ACK/NACK resource information may contain ACK/NACKresource offset information (e.g., offset ARI or ARO).

When the E-PDCCH schedules a second carrier, DL data may be received onthe second carrier in step S2304. When DL control information isreceived on the first carrier and DL data is received on the secondcarrier, the current case may correspond to the case in which crosscarrier scheduling is configured. In addition, when DL controlinformation and DL data are received on the second carrier, the currentcase may correspond to the case in which carrier schedulingconfiguration is released. According to the present invention, when theE-PDCCH schedules the second carrier, ACK/NACK resource information(e.g., offset ARI or index ARI) through a field (e.g., a TPC field) forpower transmission control information in DL control information (e.g.,a DCI field). In detail, ACK/NACK resource information may be variedaccording to an ACK/NACK transmission mode and whether cross carrier isconfigured.

According to the present invention, when cross carrier scheduling isconfigured and an ACK/NACK signal transmission mode is set as channelselection, ACK/NACK resource offset information (e.g., offset ARI orARO) may be received through a field (e.g., TPC field) for powertransmission control information in DL control information (e.g., a DCIfield).

In addition, when cross carrier scheduling is not configured and anACK/NACK signal transmission mode is set as channel selection, ACK/NACKresource indication information (e.g., index ARI) may be receivedthrough a field (e.g., a TPC field) for power transmission controlinformation in DL control information (e.g., a DCI field).

When DL data is received on the second carrier, an ACK/NACK signaltransmission mode is configured in PUCCH format 3, ACK/NACK resourceindication information (e.g., index ARI) may be received through a field(e.g., a TPC field) for power transmission control information in DLcontrol information (e.g., a DCI field).

When ACK/NACK resource offset information (e.g., offset ARI) isreceived, an ACK/NACK resource may be determined using ACK/NACK resourceoffset information and implicit PUCCH resource/index n_PUCCH linked to aspecific (e.g., lowest) eCCE index n_eCCE within a DL grantE-PDCCH/PDSCH transmission region (refer to Equation 2). For example,calculation such as addition, subtraction, multiplication, and divisionmay be performed using ACK/NACK resource offset information and implicitPUCCH resource/index n_PUCCH or other information in order to determinean ACK/NACK resource.

On the other hand, when ACK/NACK resource indication information (e.g.,index ARI) is received, the ACK/NACK resource indication information mayindicate one of a plurality of ACK/NACK resources that is pre-configuredvia, for example, a higher layer (e.g., RRC). In this case, a UE maytransmit an ACK/NACK signal using an ACK/NACK resource indicated by theACK/NACK resource indication resource. An ACK/NACK signal may betransmitted using an ACK/NACK resource indicated by the ACK/NACKresource indication resource. An ACK/NACK signal may be transmittedusing an ACK/NACK resource indicated by an index ARI. As describedabove, for example, four ACK/NACK resources may be pre-configured viahigher layer signaling (e.g., RRC signaling) and an ARI may indicate oneof the four ACK/NACK resources. In this case, the ACK/NACK resource isexplicitly indicated, and thus calculation for implicit PUCCHresource/index may not be performed. However, other calculation may befurther performed.

In an FDD situation, when an ACK/NACK transmission mode is configured inPUCCH format 3, a more detailed ARI application method is proposed asfollows for the case in which an ARI field is added to a DL grantE-PDCCH for scheduling PCC/Pcell or a DL grant E-PDCCH transmittedthrough PCC/Pcell. Since the DL grant E-PDCCH schedules PCC/Pcell or isreceived through PCC/Pcell, the current case may correspond to the casein which cross-CC scheduling is configured.

Method 4 (FDD & PUCCH Format 3)

-   -   In the case of DL grant E-PDCCH for scheduling PCC/Pcell        -   ARI transmission field: added ARI field        -   ARI application method: offset ARI    -   In the case of DL grant E-PDCCH for scheduling SCC/Scell

Method 4-1

-   -   ARI transmission field: existing field (e.g., existing TPC        field)    -   ARI applying method: index ARI    -   In this case, an added ARI field may be set as a pre-defined        fixed value (e.g., bit “0”) or set as a reserved field.

Method 4-2

-   -   ARI transmission field: added ARI field    -   ARI application method: index ARI    -   In this case, an existing field (e.g., existing TPC field) may        be set as a pre-defined fixed value (e.g., bit “0”) or set as a        reserved field.

In addition, in an FDD situation, when an ACK/NACK transmission mode isconfigured as channel selection, a more detailed ARI application methodis proposed as follows for the case in which an ARI field is added to aDL grant E-PDCCH for scheduling PCC/Pcell or a DL grant E-PDCCHtransmitted through PCC/Pcell.

Method 5 (FDD & Channel Selection)

-   -   In the case of DL grant E-PDCCH for scheduling PCC/Pcell        -   ARI transmission field: added ARI field        -   ARI application method: offset ARI    -   In the case of DL grant E-PDCCH for scheduling SCC/Scell

Method 5-1

-   -   ARI transmission field: existing field (e.g., existing TPC        field)    -   ARI application method: offset ARI    -   In this case, an added ARI field may be set as a pre-defined        fixed value (e.g., bit “0”) or set as a reserved field.

Method 5-2

-   -   ARI transmission field: added ARI field    -   ARI application method: offset ARI    -   In this case, an existing field (e.g., existing TPC field) may        be set as a pre-defined fixed value (e.g., bit “0”) or set as a        reserved field.

In a TDD situation, when an ACK/NACK transmission mode is configured inPUCCH format 3, a more detailed ARI application method is proposed asfollows for the case in which an ARI field is added to a DL grantE-PDCCH for scheduling PCC/Pcell or a DL grant E-PDCCH transmittedthrough PCC/Pcell.

Method 6 (TDD & PUCCH Format 3)

-   -   In the case of DL grant E-PDCCH corresponding to a (first) DAI        initial value (e.g., 1) while scheduling PCC/Pcell        -   ARI transmission field: added ARI field        -   ARI application method: offset ARI    -   In the case of DL grant E-PDCCH that does not correspond to a        (first) DAI initial value (e.g., 1) while scheduling PCC/Pcell        and/or DL grant E-PDCCH for scheduling SCC/Scell

Method 6-1

-   -   ARI transmission field: existing field (e.g., existing TPC        field)    -   ARI application method: index ARI    -   In this case, an added ARI field may be set as a pre-defined        fixed value (e.g., bit “0”) or set as a reserved field.

Method 6-2

-   -   ARI transmission field: added ARI field    -   ARI application method: index ARI    -   In this case, an existing field (e.g., existing TPC field) may        be set as a pre-defined fixed value (e.g., bit “0”) or set as a        reserved field.

In addition, in a TDD situation, when an ACK/NACK transmission mode isconfigured as channel selection, a more detailed ARI application methodis proposed as follows for the case in which an ARI field is added to aDL grant E-PDCCH for scheduling PCC/Pcell or a DL grant E-PDCCHtransmitted through PCC/Pcell. Hereinafter, M refers to the number of DLsubframes (i.e., DL subframes as ACK/NACK feedback target through acorresponding UL subframe) linked to one UL subframe. For example, whenM is 1, the number of DL subframes as ACK/NACK feedback target through aUL subframe is 1, when M is 2, the number of DL subframes as ACK/NACKfeedback target through a UL subframe is 2, when M is 3, the number ofDL subframes as ACK/NACK feedback target through a UL subframe is 3, andwhen M is 4, the number of DL subframes as ACK/NACK feedback targetthrough a UL subframe is 4.

In a TDD situation, when an ACK/NACK transmission mode is configured aschannel selection, even if M is 3 or more, only a PUCCH resource of thecase of DAI=1 or 2 is used for channel selection. Thus, in the case of aDL grant E-PDCCH corresponding to DAI=3 or 4, offset ARI or index ARI isnot applied.

Method 7 (TDD & Channel Selection)

-   -   M=1 or 2    -   In the case of DL grant E-PDCCH for scheduling PCC/Pcell        -   ARI transmission field: added ARI field        -   ARI application method: offset ARI    -   In the case of DL grant E-PDCCH for scheduling SCC/Scell

Method 7-1

-   -   ARI transmission field: existing field (e.g., existing TPC        field)    -   ARI application method: offset ARI    -   In this case, an added ARI field may be set as a pre-defined        fixed value (e.g., bit “0”) or set as a reserved field.

Method 7-2

-   -   ARI transmission field: added ARI field    -   ARI application method: offset ARI    -   In this case, an existing field (e.g., existing TPC field) may        be set as a pre-defined fixed value (e.g., bit “0”) or set as a        reserved field.        -   M=3 or 4        -   In the case of DL grant E-PDCCH corresponding to DAI=1 or 2            while scheduling PCC/Pcell    -   ARI transmission field: added ARI field    -   ARI applying method: offset ARI        -   In the case of DL grant E-PDCCH corresponding to DAI=1 or 2            while scheduling SCC/Scell

Method 7-3

-   -   ARI transmission field: existing field (e.g., existing TPC        field)    -   ARI applying method: offset ARI    -   In this case, an added ARI field may be set as a pre-defined        fixed value (e.g., bit “0”) or set as a reserved field.

Method 7-4

-   -   ARI transmission field: added ARI field    -   ARI application method: offset ARI    -   In this case, an existing field (e.g., existing TPC field) may        be set as a pre-defined fixed value (e.g., bit “0”) or set as a        reserved field.        -   In the case of DL grant E-PDCCH corresponding to DAI=3 or 4            while scheduling PCC/Pcell    -   no ARI application    -   In this case, an added ARI field may be set as a pre-defined        fixed value (e.g., bit “0”) or set as a reserved field.    -   an existing TPC field is used for transmission power control        -   In the case of DL grant E-PDCCH corresponding to DAI=3 or 4            while scheduling SCC/Scell    -   no ARI application    -   In this case, an added ARI field and/or an existing field (e.g.,        an existing TPC field) may be set as a pre-defined fixed value        (e.g., bit “0”) or set as a reserved field.

The ARI field configuration and the application method according to theabove proposed scheduling target CC/cell and PUCCH ACK/NACK transmissionmode, and whether cross-scheduling is present are not limited only to aDL grant E-PDCCH. For example, the proposed method can also be appliedto the case of DL grant L-PDCCH using the same/similarprinciple/operation. For example, the proposed method can also beapplied to the case in which a DL grant L-PDCCH for scheduling PCC/Pcelland a DL grant L-PDCCH for scheduling SCC/Scell are received using thesame/similar principle/operation.

So far, various embodiments have been described with regard to themethod according to the present invention. In each embodiment, somecomponents can be excluded or other components can be further added andembodiments can be implemented. In addition, these embodiments can beapplied independently or combined with each other and the embodimentscan be implemented.

FIG. 24 is a diagram illustrating a BS 110 and a UE 120 to which thepresent invention is applicable.

Referring to FIG. 24, a wireless communication system includes the BS110 and the UE 120. When the wireless communication system includes arelay, the BS 110 or the UE 120 can be replaced with the relay.

The BS 110 includes a processor 112, a memory 114, and a radio frequency(RF) unit 116. The processor 112 may be configured to embody theprocedures and/or methods proposed by the present invention. The memory114 is connected to the processor 112 and stores various pieces ofinformation associated with an operation of the processor 112. The RFunit 116 is connected to the processor 112 and transmits/receives aradio signal. The UE 120 includes a process 122, a memory 124, and an RFunit 126. The processor 122 may be configured to embody the proceduresand/or methods proposed by the present invention. The memory 124 isconnected to the processor 122 and stores various pieces of informationassociated with an operation of the processor 122. The RF unit 126 isconnected to the processor 122 and transmits/receives a radio signal.

The embodiments of the present invention described above arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim by asubsequent amendment after the application is filed.

Specific operations to be conducted by the base station in the presentinvention may also be conducted by an upper node of the base station asnecessary. In other words, it will be obvious to those skilled in theart that various operations for enabling the base station to communicatewith the terminal in a network composed of several network nodesincluding the base station will be conducted by the base station orother network nodes other than the base station. The term “base station(BS)” may be replaced with a fixed station, Node-B, eNode-B (eNB), or anaccess point as necessary. The term “terminal” may also be replaced witha user equipment (UE), a mobile station (MS) or a mobile subscriberstation (MSS) as necessary.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, an embodiment of the presentinvention may be achieved by one or more application specific integratedcircuits (ASICs), digital signal processors (DSPs), digital signalprocessing devices (DSDPs), programmable logic devices (PLDs), fieldprogrammable gate arrays (FPGAs), processors, controllers,microcontrollers, microprocessors, etc.

In a firmware or software configuration, an embodiment of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. Software code may be stored in a memory unit and executedby a processor. The memory unit is located at the interior or exteriorof the processor and may transmit and receive data to and from theprocessor via various known means.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

The present invention is applicable to a wireless communicationapparatus such as a user equipment (UE), a base station (BS), etc.

What is claimed is:
 1. A method for transmitting anacknowledgement/negative acknowledgement (ACK/NACK) signal by a userequipment (UE) in a wireless communication system, the UE beingconfigured with a primary cell (PCell) and a secondary cell (SCell), themethod comprising: receiving downlink control information (DCI) via aphysical downlink control channel (PDCCH), the DCI including a firstfield for transmit power control information and a second field forACK/NACK resource offset information; receiving downlink data via aphysical downlink shared channel (PDSCH) based on the DCI; andtransmitting an ACK/NACK signal for the downlink data using an ACK/NACKresource, wherein, when the downlink data is received on the PCell, theACK/NACK resource is determined by adding a lowest resource index of thePDCCH and a value of the ACK/NACK resource offset information, andwherein, when the downlink data is received on the SCell, the firstfield includes ACK/NACK resource indication information and the ACK/NACKresource is determined as an ACK/NACK resource indicated by the ACK/NACKresource indication information from among a plurality of ACK/NACKresources configured through a higher layer.
 2. The method according toclaim 1, wherein the UE is configured to transmit the ACK/NACK signalbased on a physical uplink control channel (PUCCH) format
 3. 3. Themethod according to claim 1, wherein the UE is configured to transmitthe ACK/NACK signal based on channel selection.
 4. The method accordingto claim 1, wherein, when the downlink data is received on the SCell,the second field is set to a predefined value.
 5. The method accordingto claim 4, wherein the predefined value is
 0. 6. The method accordingto claim 1, wherein the PDCCH is allocated in a resource region for thePDSCH in a subframe.
 7. The method according to claim 1, wherein thePCell corresponds to a cell used for the UE to establish an initialconnection and the SCell corresponds to a cell configured after theinitial connection is established.
 8. A user equipment (UE) configuredto transmit an acknowledgement/negative acknowledgement (ACK/NACK)signal in a wireless communication system, the UE being configured witha primary cell (PCell) and a secondary cell (SCell), the UE comprising:a radio frequency (RF) unit; and a processor operably coupled with theRF unit, wherein the processor is configured to: receive downlinkcontrol information (DCI) via a physical downlink control channel(PDCCH), the DCI including a first field for transmit power controlinformation and a second field for ACK/NACK resource offset information,receive downlink data via a physical downlink shared channel (PDSCH)based on the DCI, and transmit an ACK/NACK signal for the downlink datausing an ACK/NACK resource, wherein, when the downlink data is receivedon the PCell, the ACK/NACK resource is determined by adding a lowestresource index of the PDCCH and a value of the ACK/NACK resource offsetinformation, and wherein, when the downlink data is received on theSCell, the first field includes ACK/NACK resource indication informationand the ACK/NACK resource is determined as an ACK/NACK resourceindicated by the ACK/NACK resource indication information from among aplurality of ACK/NACK resources configured through a higher layer. 9.The UE according to claim 8, wherein the UE is configured to transmitthe ACK/NACK signal based on a physical uplink control channel (PUCCH)format
 3. 10. The UE according to claim 8, wherein the UE is configuredto transmit the ACK/NACK signal based on channel selection.
 11. The UEaccording to claim 8, wherein, when the downlink data is received on theSCell, the second field is set to a predefined value.
 12. The UEaccording to claim 11, wherein the predefined value is
 0. 13. The UEaccording to claim 8, wherein the PDCCH is allocated in a resourceregion for the PDSCH in a subframe.
 14. The UE according to claim 8,wherein the PCell corresponds to a cell used for the UE to establish aninitial connection and the SCell corresponds to a cell configured afterthe initial connection is established.